Comments on planned use for new chronograph

Status
Not open for further replies.

AshMan40

Member
Joined
Dec 4, 2017
Messages
57
Recently purchased my first chronograph and am interested in comments/suggestions on how to use it most effectively.

Up to now, I have used tables in reloading manuals, tables downloaded from bullet or powder manufacturer's websites as my guide when developing charges in the different calibers I reload. As I walk up my ladder developing the charges for each combo of bullet+powder I closely watch for pressure signs:
  • flat primers
  • ejector marks on the head of the case
  • craters in the primer indentation
  • blown/missing primers
  • difficulty extracting
My experience is the above signs start to appear just below the max suggested charge weights and in a few cases only after the max charge weights have been exceeded.

I've known all along that ALL charge tables come with muzzle velocity (MV) numbers that go with the suggested charges. Most boxed ammo also come with MV numbers as a measure of the expectation for the round.

I've been looking for references on using chronographs to develop reloads and there are a few that seem conflicting. I understand that MVs are not a "measure" of pressure, but it seems clear that MV is an "indicator" of whether a certain pressure has been reached, or close to it.
For example: Hornady 9th Edition shows for .223 Rem, a 24.9gr charge of CFE223 behind a 75gr BTHP bullet set at 2.250" COAL will result in a MV of 2700fps in a 20" bbl Colt AR with 1:9 twist. This is the listed max charge. In the past I work up my load and reach 24.9gr of CFE223 and see the earliest pressure signs (flat primers). Without a chrono all I know is pressure signs have just started.
Now that I have a chrono, I test the load and find the average muzzle velocity for the max load is 2600fps. Lower than expected. What does that mean?
What if the reading is 2800fps? Higher than expected. My assumption would be to lower the charge until I see 2700fps and make that my new max charge?
Note that for every bullet+powder I have previously worked up EITHER of these situations could be the case where I have reached the max listed charge (90% of the time).

Do I use my chrono readings as an "indicator" that I have reached the max charge when the MV readings match those provided in the tables (adjusting for differences like barrel length when needed)? Not all load data provides the make/specs for the rifle used so there are often assumptions that have to be made. But this is the same as boxed ammo which just give MV specs but no gun specs.

Here's a second similar question... I have load data for a powder I have previously worked up (eg. CFE223). I empty my canister and must buy a new 1lb or 8lb keg. Since it has been a while the new canister has a different lot#. Also I can no longer find the same primer brand locally so I switch to a different make but same size (sm rifle) primer. Being a safe reloader I restart my load ladder and safely reach the same max charge. My chrono tells me this new combo of powder+primer results in a different average muzzle velocity than previously. If it is a higher MV I will diligently reduce the load. But what if the MV is lower? Do I increase the charge until I replicate the previous MV. The only variable here is the powder and the primer. Unlike the comparison with a manufacturer's pressure barrel I am more confident with the suggested max load since I have already worked it up using the previous lot#.

Any comments would be appreciated.
 
A crony is just another tool for us to use. It can aid in load development but by no means use it as the governing factor. Published velocities are what they got under their test conditions and gun/test barrel. No 2 barrels are alike so always expect something different. I have 1 gun that will produce 100+fps faster with any powder when comparing data. No over pressure signs at all. Primers are a very poor indicator of pressure. So I do not use them in fact I have changed mfg due some showing over pressure signs well below max loads.
 
A chrony will do absolutely nothing to inform you of overloading. Load limits are based on peak pressure, not velocity, and individual barrels can vary 100s of fps at identical pressures.

It WILL provide interesting data on V variation, which may be helpful if the rest of your loading and shooting technique is sophisticated enough to take advantage of it.
 
Unless you can shoot "their" rifle over your chronograph .... I doubt they would .... no two rifles are the same ....
A crony is just another tool for us to use. It can aid in load development but by no means use it as the governing factor. Published velocities are what they got under their test conditions and gun/test barrel. No 2 barrels are alike so always expect something different. I have 1 gun that will produce 100+fps faster with any powder when comparing data. No over pressure signs at all. Primers are a very poor indicator of pressure. So I do not use them in fact I have changed mfg due some showing over pressure signs well below max loads.
A chrony will do absolutely nothing to inform you of overloading. Load limits are based on peak pressure, not velocity, and individual barrels can vary 100s of fps at identical pressures.
Thanks all for your comments. I fully get the idea that even IF you owned the SAME rifle as used in the testing AND all your components were the same make/type... you STILL may not get the same pressure or MV.

The point on peak pressure measurements taken during manufacture testing and provided for reference... WHO has a system to test pressure at their disposal in the caliber they shoot? "No one" I know of, so having that data is only useful to know the manufacture reached (or remained below) the SAAMI spec when they stopping increasing their charge weights. And at THAT pressure they reached the specified MV. Some reloading tables (like the Hornady manual) doesn't even provide pressure data only an indicator that the charge/MV was the "Maximum load". In fact the Hornady data has typically been conservative when compared with the Hodgdon load data which lists charge+MV+pressure and typically has a much "hotter" max load. Again, the combination of rifles and reloading components were different so a direct comparison is not always possible.

What that means is that WE (the general populace who reload in our basement/garage) only have MV data and the various pressure signs I listed above as our "indicators" of pressure. So, now that I have a chronograph, do I add MV to my list of "pressure indicators"?? And use it along side (not in place of) the other pressure signs?

For example, Blue68f100 mentions above his rifle produces MV 100+fps than the reloading data even before pressure signs. Depending on the data he is using, should he STOP progressing his load when he reaches the MV of the max charge even if he is using a lower charge and no other pressure signs are present?

A better example might be the Hornady .vs Hodgdon load data. Hornady has a max charge which produces a 2800fps MV using a specific Hodgdon powder. The same weight bullet in Hodgdon's load data has a max charge 0.9gr higher going 200fps faster at the muzzle. If I reach Hodgdon max MV before I reach the Hodgdon max charge do I stop even if there are no other pressure signs? My gut says STOP based on the max MV and not wait to also see pressure signs on the case head, or elsewhere.

In my case, my new T/C Compass in .308WIN has a problem with ejector marks on almost EVERY case. It could be a defect in the bolt face. These marks are there even before the primers start to flatten. If I only used ejector marks as a pressure sign I would never get much higher than the starting loads. But I know the pressures are approaching max when the primers start to flatten. My point is, if I see max MV speeds before I see any other pressure signs do I stop progressing my ladder. Or do I continue until I see the more traditional pressure signs...or until I reach the max listed charges (this was my old method BEFORE purchasing a chrono)? It raises the question of the safety of NOT having a chronograph to compare the MV if you can reach the listed max MV before other pressure signs.


I'm trying to establish my new protocol now that I have MV data to compare with the reloading tables. Do I now stop increasing the charge weights when I reach max MV OR when I see the traditional visual pressure signs... which ever comes first? That would seem safest, but also suggest that I use MV as a "pressure indicator" (or pressure sign). Ideally I'd use peak pressure, if I had the equipment to measure it, but I don't.
BTW, I'm also cataloging the MV of boxed ammo thru my rifles and comparing the MV of my handloads of the same bullet weight. The boxed ammo MV will likely become the new max MV for my loads... assuming it less than the reloading data.
 
Last edited:
I look at it like this...I’m a lot more concerned with how the load performs. Pressure signs- sure. But otherwise, how does it function, how does it group. If my chrony data said my SD was sky high, but I had an moa group at 300 yds, I wouldn’t care.

For my 223 ammo I loaded for storage for zombies or whatnot it was useful. I wanted every bit of FPS I could wring out and still be safe since velocity is a concern for 55gr terminal performance. Otherwise, I’m limited to 300 yds at my range. So I don’t really need chrony for data to figure out a range card - I can just shoot it.

But a box of factory ammo says it does x,xxx FPS....I don’t really care. Load data says it does y,yyy FPS again don’t care. Neither is the truth. How fast is mine going? Once again, usually don’t much care.

One example of when I did appreciate the chrony and leaned on it pretty heavy was working down my 300blk subsonic load. I wouldn’t have wanted to be guessing there.

I have Hornady 8th Ed. It is probably the most conservative of all my references in general. I wouldn’t try to use chrony data to reconcile hornady data with hodgdon....you will find some cases that reference A max load is the starting load for ref B.

Reading primers as a gauge of excess pressure is kind of iffy. A lot of that depends on the primer itself. It’s a clue, but not hard evidence. Alone with no other signs, I’d almost discount it. You’ll see a lot of factory ammo even give you a flattened primer and decent ejector circle mark esp with milsurp. What you will most likely really notice first is the violent extraction. Before you’ve even seen the results on the primer and brass, you got that feedback.

But really, since you’re talking 223 and an AR, what is your goal for the load? Max possible FPS? I sound like an idiot saying it since that is what I did at first and wanted to put that away as hot as I could get it within reason, but years later I realize that was dumb. A case of LC or Q3131would have been just fine to put up. My current loads are toward the lighter side. For general training fmj ammo think wolf wpa type speeds. My precision loads are even slower since once I hit a good accy node, I stopped....no need making the bullet go faster if it can hit a 2” target at 300 yds all day long.

Sorry, but I’m not sure what you’re expecting with the newly added data from the chrony? You’re really gonna get upset when you run a load worked up in the winter over the chrony in August . Sure, measure your stuff just so you know how fast it’s running, have the precise data for QL if you use that, calculate sd to give you an idea of how consistent your process is, or make sure a sub load is where it needs to be, but otherwise how are you using the data? What you mentioned so far doesn’t sound like what you should be using it for to me.....
 
@AshMan40, I see a lot of talk about velocity and nothing about accuracy. It seems the velocity craze is still getting worse every year. When you are half way up the pressure curve start looking for the most accurate load and go with it. Most times an additional 100 fps will deliver nothing better that the accurate load that is slightly slower. All the velocity in the world will do nothing for you unless you make good hits on game.

BTW more times than not flattened primers do not mean your load is over pressure. Developing higher velocities than in the load manual with different components doesn't always mean you are over pressure either.
 
@AshMan40, I see a lot of talk about velocity and nothing about accuracy. It seems the velocity craze is still getting worse every year...All the velocity in the world will do nothing for you unless you make good hits on game.

Exactly this. If you are concerned about getting terminal performance out of a 55gr .223, use a bigger caliber. In my experience low to mid-range charges are the most accurate. They have the added bonus of being easier on your rifle, brass, and you can squeeze a few more rounds out of the bottle.

If you can't hit the target it doesn't really matter how fast the miss was going. MV is only one aspect of velocity to consider, I would be more concerned about about retained velocity downrange.

.40
 
Last edited:
I always thought the chrono was more for calculating energy or bullet drop at different ranges. I think sometimes we get hooked into chasing numbers. I am guilty.
 
Another 100/200 FPS at the expense of over pressure is not worth it. By the time you see ejector marks and blown primers you are way over pressure, and they surely shouldn't be happening below max from published pressure tested loads unless you have something a lot different in your mixture of components. A chrono is a useful tool, but it doesn't read pressure.

I see way to much lack on concern for pressure in general in print on the internet. Y'all be careful out there. Oh, and get a bigger gun if you thing you need more power.
 
What that means is that WE (the general populace who reload in our basement/garage) only have MV data and the various pressure signs I listed above as our "indicators" of pressure. So, now that I have a chronograph, do I add MV to my list of "pressure indicators"?? And use it along side (not in place of) the other pressure signs?

I had a Winchester 70 .25/06 with a 24" barrel . .. I have a Browning A- Bolt . 25/06 with a 22" barrel ...

The Win 70 will shoot a load of IMR 7828 and a 115 Nosler BT to about 2980 fps ....
The A-Bolt will.shoot the same load to about 3150 fps ...
Both primers look about the same .... Both appear safe ....one is just faster.... the A-bolt more accurate...

Pact Model One Chronograph used for both ....

By using the velocities ..... How would I determine "pressure" ???
 
I place mine at 15'. Any thing less, I've had some strange readings and misses. ProCrony Digital. I use the sun screen supports and shade as a tool for aligning it up with the bore. Setup like your going to shoot, then set your crony up. I've used a laser bore sighter to aide in setup in the past. With it you know the path of the bullet is taking over the unit. I try to keep the center as close as possible. as you get to the outer edges you will start dropping shots.
 
Recently purchased my first chronograph and am interested in comments/suggestions on how to use it most effectively.

Up to now, I have used tables in reloading manuals, tables downloaded from bullet or powder manufacturer's websites as my guide when developing charges in the different calibers I reload. As I walk up my ladder developing the charges for each combo of bullet+powder I closely watch for pressure signs:
  • flat primers
  • ejector marks on the head of the case
  • craters in the primer indentation
  • blown/missing primers
  • difficulty extracting
My experience is the above signs start to appear just below the max suggested charge weights and in a few cases only after the max charge weights have been exceeded.

I've known all along that ALL charge tables come with muzzle velocity (MV) numbers that go with the suggested charges. Most boxed ammo also come with MV numbers as a measure of the expectation for the round.

I've been looking for references on using chronographs to develop reloads and there are a few that seem conflicting. I understand that MVs are not a "measure" of pressure, but it seems clear that MV is an "indicator" of whether a certain pressure has been reached, or close to it.
For example: Hornady 9th Edition shows for .223 Rem, a 24.9gr charge of CFE223 behind a 75gr BTHP bullet set at 2.250" COAL will result in a MV of 2700fps in a 20" bbl Colt AR with 1:9 twist. This is the listed max charge. In the past I work up my load and reach 24.9gr of CFE223 and see the earliest pressure signs (flat primers). Without a chrono all I know is pressure signs have just started.
Now that I have a chrono, I test the load and find the average muzzle velocity for the max load is 2600fps. Lower than expected. What does that mean?
What if the reading is 2800fps? Higher than expected. My assumption would be to lower the charge until I see 2700fps and make that my new max charge?
Note that for every bullet+powder I have previously worked up EITHER of these situations could be the case where I have reached the max listed charge (90% of the time).

Do I use my chrono readings as an "indicator" that I have reached the max charge when the MV readings match those provided in the tables (adjusting for differences like barrel length when needed)? Not all load data provides the make/specs for the rifle used so there are often assumptions that have to be made. But this is the same as boxed ammo which just give MV specs but no gun specs.

Here's a second similar question... I have load data for a powder I have previously worked up (eg. CFE223). I empty my canister and must buy a new 1lb or 8lb keg. Since it has been a while the new canister has a different lot#. Also I can no longer find the same primer brand locally so I switch to a different make but same size (sm rifle) primer. Being a safe reloader I restart my load ladder and safely reach the same max charge. My chrono tells me this new combo of powder+primer results in a different average muzzle velocity than previously. If it is a higher MV I will diligently reduce the load. But what if the MV is lower? Do I increase the charge until I replicate the previous MV. The only variable here is the powder and the primer. Unlike the comparison with a manufacturer's pressure barrel I am more confident with the suggested max load since I have already worked it up using the previous lot#.

Any comments would be appreciated.
I have found Hornady data with CFE 223 to just be flat out wrong. See here:
Dom
 
Reading primers as a gauge of excess pressure is kind of iffy. A lot of that depends on the primer itself. It’s a clue, but not hard evidence. Alone with no other signs, I’d almost discount it. You’ll see a lot of factory ammo even give you a flattened primer and decent ejector circle mark esp with milsurp. What you will most likely really notice first is the violent extraction. Before you’ve even seen the results on the primer and brass, you got that feedback..
This rather contradicts what I have been working from. Lacking an actual rig that can measure the pressure in the barrel, indicators (primers, ejectors, etc.) are all I have had up to now. My queries are really about adding MV as an additional indicator, or not. If I discount primer condition as a sign of pressure I'm a bit concerned that by the time I see ejector marks I'm much closer to max pressures than I want to get. Violent extraction is not something I'm used to seeing in ANY of my AR handloads. Up to now, the typical progression I see is flat primers, cratered primers and then ejector swipes as I approach (or in some cases exceed) the recommended max loads. When I've gone too far I get blown primers or primers that are extending out from the case head. This was all before I had my chrono.

How to blend in the additional knowledge of the matching MV that goes with that load to make better choices? Do I stop the load progression when I reach the recommended max load MV even without ANY pressure signs? In the past I wouldn't have had the MV data to know I should stop, but now I do. Do I treat it like flat primers? It is one more indicator I am close to that max pressure, but maybe not yet there since I'm not seeing the OTHER signs.

In case you are wondering, I'm NOT after max MV. What I'd really like is to use MV to measure consistency but also if by using it as an additional pressure indicator it allows me a (safe) wider range to test for the most accurate loads. Increasing the range increases my chances of finding the BEST charge that works for my rifles.
For example, if using traditional pressure signs I stop my load progression 1.0gr below the listed max charge. Within this smaller available range I find a good load that gets me consistent 1.5MOA groups. If the chrono MVs allow me to safely tap into the range right up to max load (or closer to it) and in there I find a load that consistently produces 1.25 or 1.0MOA groups I would be very happy! Right now I'm limited when the tarditional pressure signs tell me to stop short of the max load. I don't know if that max load is already over the max MV, or is there still head room?

BTW, I typically find that military loaded rounds (M193, M885) "feel" hotter than factory loads. Flat primers and ejector swipes are the norm with these rounds. Some of the listed MVs for these rounds also support that they are faster than other boxed ammo. So military rounds will likely be my max MVs (especially when loading into LC cases). In some cases I have load data to replicate military/NATO rounds. I'd like to use my chrono to confirm this by comparing the MV from boxed NATO rounds with the worked up loads that are supposed to replicate them.


I had a Winchester 70 .25/06 with a 24" barrel . .. I have a Browning A- Bolt . 25/06 with a 22" barrel ...

The Win 70 will shoot a load of IMR 7828 and a 115 Nosler BT to about 2980 fps ....
The A-Bolt will.shoot the same load to about 3150 fps ...
Both primers look about the same .... Both appear safe ....one is just faster.... the A-bolt more accurate...

Pact Model One Chronograph used for both ....

By using the velocities ..... How would I determine "pressure" ???
My initial thought was your example was an apples-to-oranges comparison but you are talking about the exact same load used in two different guns so the only variables are the guns and not your reloading. I guess I would add a 3rd variable... a factory loaded round with a similar weight/profile bullet. Fire it through both rifles and see how your handload compares to the factory boxed load. If your MV is higher, you are generating more pressure than the factory load. This is also what I am working on bulding a table of factory ammo MVs to work with. While some load data suggests I could create loads with a higher MV I'd probably play it safe and stick to the same (or less) MV as boxed ammo. Again, prior to my chrono I didn't have this option.

Here is what my "simple brain" is thinking.... factory ammo produces a MV of 2800fps. My handload produces MV of 2850fps. My handload is producing MORE pressure. Obviously, the powders, primers and cases between the two rounds are different and are affecting HOW that pressure is building behind the bullet in the barrel. But to reach 2800fps from a dead stop that bullet had to be accelerated by a certain amount by the pressure behind it. My round that came out at 2850fps had to have MORE acceleration to result in a higher MV. If I am still below the max load and there are no pressure signs I can stay where I am or choose to lower the powder charge until I get 2800fps like the factory round and feel even more confident I am not over pressuring. Without the chrono to compare the rounds I wouldn't know if my handload was faster/slower.

One example I can quote from my Hornady manual is when varying the COAL to reduce/increase the distance the bullet must travel before contacting the lands in the barrel. Here the rifle and cartridge are all constant. Increase the distance (shorter COAL) and the peak pressure goes down and you see lower MV. Reduce the distance to the lands (longer COAL) and you get increased pressure and higher MV because the bullet had no free space to jump forward as the pressure increases. The Hornady manual suggests that seating the bullet just shy of the land will get the best precision, but you need to adjust the powder load DOWN to reduce the pressure caused by the reduced distance.
My thought is that in this case you identify the MV when the bullet is seated at recommended length for the load or max COAL from the manual (safe pressure). Note the increased MV when you increase the COAL to minimize the jump and reduce the powder charge to bring you back to where you were. In this example the MV IS an indicator for more pressure and dialing down the MV until you are back down where you started is compensating for the increased pressure caused by the longer COAL. You change one variable and note a MV change. It MUST mean a pressure increase/decrease, right? Then dialing down the MV is again using MV as a pressure indicator.

I've not tried this yet as I haven't had time to do this with my new bolt-action .308, but it is planned. This type of experimentation doesn't work for my ARs as I hit max magazine length before the bullets get close to the lands.


I place mine at 15'. Any thing less, I've had some strange readings and misses.
I placed my chrono at around 10ft and was getting errors related to different readings between the two sensors. I'll try backing it off to 15ft next time and see if it works better.
 
Last edited:
This rather contradicts what I have been working from. Lacking an actual rig that can measure the pressure in the barrel, indicators (primers, ejectors, etc.) are all I have had up to now. My queries are really about adding MV as an additional indicator, or not. If I discount primer condition as a sign of pressure I'm a bit concerned that by the time I see ejector marks I'm much closer to max pressures than I want to get. Violent extraction is not something I'm used to seeing in ANY of my AR handloads. Up to now, the typical progression I see is flat primers, cratered primers and then ejector swipes as I approach (or in some cases exceed) the recommended max loads. When I've gone too far I get blown primers or primers that are extending out from the case head. This was all before I had my chrono.

How to blend in the additional knowledge of the matching MV that goes with that load to make better choices? Do I stop the load progression when I reach the recommended max load MV even without ANY pressure signs? In the past I wouldn't have had the MV data to know I should stop, but now I do. Do I treat it like flat primers? It is one more indicator I am close to that max pressure, but maybe not yet there since I'm not seeing the OTHER signs.
....

I'm not contradicting anything - I'm saying reading a primer with no other indications - is iffy. Might be telling you something, might just be what that primer does. Violent extraction.....shoot some factory Aguila or Wolf WPA - both of those are toward the milder end of things. Note the extraction. Then switch to Q3131A or IMI M193. If your loads are ever extracting "more violently" than those, that's instant feedback that something is off. I don't mean they're gonna launch a mile or anything, but you will notice the difference between mild & violent and what's in between. Again, that is a lone indicator, and you see it along with some others, you have an issue.



Capture555.gif

Capture777.gif
Capture6666.gif

I use different powder than you (H335), but 3 references. Hodgon & Speer - same projectile, same powder, almost same length, but different data. Which MV would you be chasing with your chrony???? Hodgon's higher # with a lighter charge or Speer's lower MV# with a higher charge? Then throw Hornady in the mix. Different but fairly similar bullet - your starting loads for 2 sources are max load for another. Do you chase Hornady or Speer's MV? oh they're the same....hmmm now what? See where I'm going?

I can tell you this much - I can't come close to Speer's max load. Hodgdon's is right on the edge for me - I wouldn't go further. And that Hornady 2266 bullet needs 24.6ish gr to shine for me - and that's not a hot load for it even though it goes 6% over their max - lot of people loading that bullet a little more than I am.
 
My initial thought was your example was an apples-to-oranges comparison but you are talking about the exact same load used in two different guns so the only variables are the guns and not your reloading. I guess I would add a 3rd variable... a factory loaded round with a similar weight/profile bullet. Fire it through both rifles and see how your handload compares to the factory boxed load. If your MV is higher, you are generating more pressure than the factory load.

How can you conclude that just because of higher velocity ... You'd have higher pressures ....??

You can't!!! Unless you have a method to measure pressure ...
 
All of my AR's have min spec match barrels, adj gas blocks. When I'm working up a load I really don't care what the velocity is, accuracy trumps. In most all cases though if I'm shooing a match bullet my loads are at near max, at max or over, all depends on the gun and powder being used. With my match rifles I have loads that are 1 moa or less depending if I do my part. When testing though I use a Lead Sled and single feed with a bob sled. This way I get to look at each round after firing for evaluation. Single feeding eliminates any damage to the bullets. Once I've got my load I then tweak the OAL to see if I can tighten the groups up. Followed with trying different primers.

With some calibers (6.5 CM) there are know nodes in velocity you need to be in for the best accuracy. The 224 V is similar but a lot more sensitive due to smaller case volume.

A lot of times it pays to do a blind test. By this I mean leave all the test parameter at the bench and assign a code. Also the order in which you shoot can and will create problems depending on fouling. I normally do not shoot 1 load up before moving to the next. I shoot 1 of each and progress changing the starting once each round. This alone with using the bob sled gives some time for the barrel to cool, and spreads the fouling out so it's ever between all groups.

The only time I about a group is when pressure signs show up. Either in the primer or brass.
 
Read up on positive compensation and you will give up on any notions that a specific increase in velocity after a relatively flat span of velocities means anything significant in terms of pressure. Velocity ladders to reveal nodes tell you far more about harmonics than about peak pressure.
 
Recently purchased my first chronograph and am interested in comments/suggestions on how to use it most effectively.
Congratulations! The chrono helps fuel the addiction. I didn't see what brand you purchased, but since you placed it at 10' I'm guessing it's a shoot through version. I have the CED pro with Bluetooth and a Labradar. The CED for me works best with the sky screens, and either a bright day/blue sky or bright overcast. When clouds are moving ahead, sometimes it misses. Don't have one sensor in the shade and one in the sun - either both in or out helps. Try to keep the bullet path straight through the two sensors as any angle will skew the calculated velocity.
I place the CED 15' from the shooting bench to minimize muzzle blast effects. I place a target directly behind the CED so it gives me an aiming point, and I try to get the bullet path 6" over the sensors. I also bench the rifle or pistol and made a boo boo plate to protect the plastic chrono. Don't sit on your spurs and don't shoot your chrono.
I buy 300-400 rounds of a factory ammo and use that as my "calibration" ammo. I shoot 5 or so rounds as the first string every chrono session and compare that to previous sessions, just to make sure the chrono is measuring consistently. There's no good way to know how accurate it is, or how fast the factory ammo is in a particular firearm, but if they do publish a velocity figure and your chrono is significantly different, find someone close by who has another chrono. Everyone will jump on the "significant", so figure out something that's reasonable to you - for factory ammo I use 10%.

There is a relationship between MV and Pressure. The problem is it's non-linear and non-determinate, at least for us mere mortals. I do pay attention to the published min max numbers, and for example, I am working on a .243 load where a below minimum starting charge resulted in an above maximum velocity. Others on the forum don't see this as an issue, but, I do. There were no obvious pressure signs but since I can't measure pressure and I can measure velocity and this velocity was above where I felt I needed to be, I stopped. I don't need to chase high MVs.

Sounds like you're doing rifle currently. If you ascribe to the accuracy node theory, you can at least determine the velocity at the nodes. You can than insure subsequent loadings are matching that velocity. If you ascribe to the velocity plateau theory, you'll see that data from your chrono and then can once again insure your loadings fall at those velocities. There's some common thinking that at some point in the load data the velocity won't change drastically from different charges so there's some insensitivity of powder charge weight. If you're in to long range rifle, the MV, SD and ES numbers are more important once you're dialed in to a specific load. Don't fall in to the trap of the lowest SD will result in the most precise load - it may, but then again it may not. And from a pure statistics point of view a lot of the data we gather probably doesn't have the population size necessary for a statistically significant conclusion. Having said that, I'm happy looking at my numbers be it n=5 for rifle or n=10 for pistol.

For pistol, the chrono helps assure me the loads are making a specific power factor. The SD and ES numbers are interesting but again, not necessarily indicating a precise load. I use the SD as a QC measure of my process and consistency across a production lot of pistol ammo. You may want to take some time and think about how you collect and organize all this data as over time it becomes voluminous.

Have fun with your new toy and don't forget there are other fast moving things you can send across it to measure!
 
I'm not contradicting anything - I'm saying reading a primer with no other indications - is iffy. Might be telling you something, might just be what that primer does. Violent extraction.....shoot some factory Aguila or Wolf WPA - both of those are toward the milder end of things. Note the extraction. Then switch to Q3131A or IMI M193. If your loads are ever extracting "more violently" than those, that's instant feedback that something is off. I don't mean they're gonna launch a mile or anything, but you will notice the difference between mild & violent and what's in between. Again, that is a lone indicator, and you see it along with some others, you have an issue.
Now I DO agree with you that factory loaded rounds (off the shelf or milsurp) that flatten primers cannot on its own be taken to mean excessive pressure with no other indicators. But this is not the same as watching the changes in primer shape as you work up a load.
My normal load ladders start low. So low that the starting loads normally show no pressure signs. The primer+case head looks identical to a newly loaded cartridge except it has a dimple in the middle of the primer. As the powder charge increases (everything else the same) I start to see the shape of the primer flatten. The edges of the primer start to take on more of a right angle. The face of the primer takes the texture of the bolt face. As the pressure increases, eventually the primer fills the gap between the primer and case head creating an almost completely flat surface across the case head. This progression of flattening is definitely a sign of increased pressure without any other visible signs of over pressure and occur close to the listed max load from the various tables. Regardless of whether I see ejector marks or other indicators, once the primer fills the gap in the case head I stop my progression. That is the limit of what I feel comfortable with... and typically my goal is to reload my cases multiple times so pushing the max pressures is counter productive.
So I'm confused how you can say primer changes alone cannot indicate pressure, at least when it comes to reading reloads. Now this is primarily my experience with reloading .223/5.56NATO cases so I don't know how well it translates to other cases and other size/thickeners primers. I’m assuming military-style primers are thicker so can take more pressure before flattening. I'm just starting to reload large rifle primer .308/7.62NATO cases. I've spent most of my time over the last few years working with CCI and Winchester small rifle primers in my 223 and 300 BLK rifles.


I use different powder than you (H335), but 3 references. Hodgon & Speer - same projectile, same powder, almost same length, but different data. Which MV would you be chasing with your chrony???? Hodgon's higher # with a lighter charge or Speer's lower MV# with a higher charge? Then throw Hornady in the mix. Different but fairly similar bullet - your starting loads for 2 sources are max load for another. Do you chase Hornady or Speer's MV? oh they're the same....hmmm now what? See where I'm going?
This is something I ran into recently starting my handloads for .308WIN. I started with the suggested starting load from the Hodgdon load table for my powder (CFE223). I now know this was a bad idea. Instead, I should have started 10% lower than the max listed load which is the common suggestion. Or maybe I should have started with the Hornady load data (lower start/end charges) which maxed out at Hodgdon's starting charge. My starting load was stiff extracting and by the 2nd step in the ladder the fired cartridges were stuck in the chamber (bolt action). It's not as simple as saying the starting charge was too hot. It may have been but there is more to my problems. My Lee sizing dies apparently created cases slightly larger than SAAMI minimum resulting in newly sized cases getting stuck in the chamber. I confirmed this later by chambering newly resized cases into the chamber and they would get stuck as well. I also discovered a broken extractor in the bolt head. This has been sent back for repair. Did the bad resizing die cause the case to get stuck? Did the stuck case cause the extractor to break? Was it over pressure that caused the case to get stuck?? Was it just a perfect storm of unlikely causes?


How can you conclude that just because of higher velocity ... You'd have higher pressures ....??

You can't!!! Unless you have a method to measure pressure ...
I'm not clear if you mean that getting a MV reading off an arbitrary hand load (or boxed ammo) can't be used to judge how close you are to max pressure... I can agree with that. But getting a MV from a known safe reference (boxed ammo with same bullet weight/shape as your hand loads) is a known point of reference in your rifle. This is based on the idea that EVERY factory loaded round (to SAAMI spec) will NOT produce unsafe pressured in ANY SAAMI spec rifle (no need to bring up the NATO vs SAAMI argument as this is a specific case which if known of can be mitigated). This is the principle of having a spec like SAAMI.
This is not the same as a listed load+MV as this listed MV is will likely NOT be the same in your rifle.

But if you are saying a change in MV following a single change (eg. increase in powder charge or change in COAL), does NOT indicate an increase in pressure... I'm gonna take the opposite side of that argument. My reference above to page 25 in the Hornady 9th edition describes how just a change in the COAL can result in increase/decrease in pressure which shows up as increased/decreased MV. In that specific case, MV IS an indicator of increase/decreased pressure without a pressure gauge.

Typically, I look for the powder that gives me the widest range of bullet types/weights, but also leaning towards the powder that returns the highest velocities within any weight. The reason for this is the powder gets me the most headroom. As others have suggested, I tend to find the best loads (smallest grouping) is near the top end of the MV, but not necessarily AT max MV. Now that I have a chrono, it also means I don’t have to worry as much if I’m getting close to the factory MV.

For example, here is what I am thinking of doing... I take a NEW box of Federal Fusion .308 165gr SPBT which is rated at 2700fps. I fire it thru my rifle and find the MV average is actually 2600fps. Now I have an actual reference point that is specific to my rifle. This is making the assumption the boxed ammo does NOT create unsafe pressures in my rifle.
I’m reloading Speer 165gr SPBT bullets over CFE223 which the Hodgdon data says max load of 48.3gr will produce a MV of 2839fps @61,500psi. This just tells me I have overhead room and should be able to safely reach the 2600fps MV that the Federal ammo hit using CFE223. If I chose a different powered that had a max MV of less than 2600fps I would have an issue. This is why choosing a powder that reaches higher MVs is key. I work up my loads looking to recreate the same 2600fps and remain below the max listed charge, looking for pressure signs along the way. If I reach 2600fps and see no other pressure signs I could try increasing the charge slightly. But if I find a sweet spot before 2600fps I can go with it. Once I have this reference MV, I can start to work the COAL and seat the bullet just shy of the lands and reduce the charge to maintain the MV.
This is only possible because I can get a MV reference from the boxed ammo and work around it as a safe example fired in my rifle.

Is there a flaw in this process that makes it unsafe? Note, review the above process and consider how you could do it w/o a chrono? You really can’t. You’d just increase the powder charge until you either reached the charge that had the same listed MV (2700fps) or until you started to see pressure signs. Having the chrono allows a different approach with actual comparisons.
Appreciate any feedback.
 
Is there a flaw in this process that makes it unsafe?
Yes. You’re assuming the Federal Fusion Factory ammo powder/primer/case/bullet/COL are equivalent to your powder/primer/case/bullet/COL. I don’t know what powder Federal uses, but I’d bet a beer it’s not CFE223. You shouldn’t presume an MV equates to a safe pressure. The pressure curves from different powder burns are different. Different curves can still produce the same MV.
 
Now I DO agree with you that factory loaded rounds (off the shelf or milsurp) that flatten primers cannot on its own be taken to mean excessive pressure with no other indicators. But this is not the same as watching the changes in primer shape as you work up a load.
My normal load ladders start low. So low that the starting loads normally show no pressure signs. The primer+case head looks identical to a newly loaded cartridge except it has a dimple in the middle of the primer. As the powder charge increases (everything else the same) I start to see the shape of the primer flatten. The edges of the primer start to take on more of a right angle. The face of the primer takes the texture of the bolt face. As the pressure increases, eventually the primer fills the gap between the primer and case head creating an almost completely flat surface across the case head. This progression of flattening is definitely a sign of increased pressure without any other visible signs of over pressure and occur close to the listed max load from the various tables. Regardless of whether I see ejector marks or other indicators, once the primer fills the gap in the case head I stop my progression. That is the limit of what I feel comfortable with... and typically my goal is to reload my cases multiple times so pushing the max pressures is counter productive.
So I'm confused how you can say primer changes alone cannot indicate pressure, at least when it comes to reading reloads. Now this is primarily my experience with reloading .223/5.56NATO cases so I don't know how well it translates to other cases and other size/thickeners primers. I’m assuming military-style primers are thicker so can take more pressure before flattening. I'm just starting to reload large rifle primer .308/7.62NATO cases. I've spent most of my time over the last few years working with CCI and Winchester small rifle primers in my 223 and 300 BLK rifles.

What do you think those commercial ammo primers might look like with a couple tenths less charge? I got a hold of some Hornady factory 300BLK that was overpressure. Showed more than a flattened, cratered primer. But first indication something was way off was violent extraction & recoil feel. But if you wouldn't pick up a factory spent case with a flattened primer, no other indications it was overpressure, why would you assume a reload is with exact same conditions?

But you are misinterpreting or I am writing unclearly. I am not saying a flattened primer is not a sign of an overpressure load. I am saying a flattened primer alone - with nothing else to accompany it to indicate the round is overpressure - could very well be just how that primer behaves at normal pressures that are somewhere between a starting load and max. Reading primers alone - without any other information at all - is not reliable evidence that you are or are not in an unsafe place.

Demonstrate this for yourself. Back off 2/10 from where you are now with whatever components you are using. Then load a couple rounds each with CCI #41, CCI #400, WSR, and Rem 7 1/2. They'll probably all appear slightly different - they're going to behave differently.

Yes, you will see differences in primer with increased loads - I didn't say you should not. But what you are describing is normal and may simply be a sign of increased pressure, not necessarily overpressure.

It almost seems to me that you want to figure out a way to say "once my primer starts looking like a typical commercial primer I want to run that load over my chrony and let the FPS # it displays dictate if I should stop or keep going". That isn't going to work no matter how many times you rephrase the question. I may be off, but that's how I would best summarize how I read it.


This is something I ran into recently starting my handloads for .308WIN. I started with the suggested starting load from the Hodgdon load table for my powder (CFE223). I now know this was a bad idea. Instead, I should have started 10% lower than the max listed load which is the common suggestion. Or maybe I should have started with the Hornady load data (lower start/end charges) which maxed out at Hodgdon's starting charge. My starting load was stiff extracting and by the 2nd step in the ladder the fired cartridges were stuck in the chamber (bolt action). It's not as simple as saying the starting charge was too hot. It may have been but there is more to my problems. My Lee sizing dies apparently created cases slightly larger than SAAMI minimum resulting in newly sized cases getting stuck in the chamber. I confirmed this later by chambering newly resized cases into the chamber and they would get stuck as well. I also discovered a broken extractor in the bolt head. This has been sent back for repair. Did the bad resizing die cause the case to get stuck? Did the stuck case cause the extractor to break? Was it over pressure that caused the case to get stuck?? Was it just a perfect storm of unlikely causes?

I have no idea how experienced you are reloading in general, so forgive me if I seem condescending (we're all here to learn something new). But #1 there is don't just start with a single data source & run. Starting something new, consult several & see where they agree, overlap. That one source, although unlikely, could be way wrong. For a 168gr projectile, starting load and max -10% in your case is almost same.

I'm not sure about the "start -10% from max" rule of thumb comes from. "-10% from what you have now" for a small component change I've heard often. Or following some other recipe that only gives a single charge. But in general, not sure why -10% from max would be better than the published starting load - to me that sounds like trust one number, not the other. You wouldn't reverse that and say starting load +10% is max load....But it might be a thing that's common.

What did your case gauge say about the resized brass?
 
Yes. You’re assuming the Federal Fusion Factory ammo powder/primer/case/bullet/COL are equivalent to your powder/primer/case/bullet/COL.
Actually that is NOT my assumption. I realize we rarely know the powder and primer used for any boxed ammo and there is nothing to prevent the manufacturer from changing the variables at any time. They have the resources to vary anything but adjust to get the same MV and pressures as their rounds are designed to produce.
My “assumption” are two:
1) Boxed ammo from a major manufacturer will NOT produce unsafe pressures (or will comply with SAAMI standards).
2) If a boxed ammo (with a bullet as close to my reloaded bullet weight/style as I can find) produces a MV within the range my reloading data says my powder+bullet combination is capable of (with some headroom for a measure of safety) I will be able to work up a load to try and achieve the same MV. If I reach that MV before I see other pressure signs... I’m good and this load does not exceed a safe pressure. I know the acceleration is the same as the bullet has reached the same MV. Are the pressures that created that acceleration the same?? I don’t know, likely NOT as the pressure curve will differ by powder/case/primer. But is this a SAFE pressure?
The safety comes with staying within the load data tables and still looking for pressure signs along the way. The factory MV is just one more variable to add while working up the load.
This assumption DOESN’T work if the data for the powder selected does NOT reach and exceed the MV of the factory ammo. It WOULD be dangerous to try and get such a powder to produce the factory round MV. This is NOT what I’m suggesting.

The only data usually available for boxed ammo is the bullet weight, shape AND the advertised MV. Honestly, if you don’t actually pull a bullet and weigh it you are assuming it matches what’s on the box. How many people actually pull the bullets for a box of ammo they buy off the shelf to make sure the weight is as advertised? Not me. The advertised MV is NOT the reference point. It may only be useful when trying to select a powder that can produce that MV for the bullet weight. The actual MV that is measured thru your individual rifle is the reference point.
Can known MV (MV produced on my rifle) data be used to improve the handloads? I supposed that is the crux of my question. Does it help to use boxed ammo as a fixed reference point in addition to load data from multiple sources (that sometimes conflict)?
I see this as a similar exercise to a bullet manufacturer saying the terminal ballistic for their particular bullet is most effective once you have reached a specified MV (or a calculated MV based on the desired velocity at the target distance). You develop your load to try and reproduce the manufacture’s MV. You select a powder that can reach and exceed that target MV. You work up the load while watching for other pressure signs and stop when you reach it of slightly exceed it. The difference is here you are trying to reach and advertised MV for optimum performance, vs. trying to reach a confirmed MV based on tested data. I also expect the performance MV would be lower than the factory ammo MV since the bullet would be for use over a wide range of velocities.


But you are misinterpreting or I am writing unclearly. I am not saying a flattened primer is not a sign of an overpressure load. I am saying a flattened primer alone - with nothing else to accompany it to indicate the round is overpressure - could very well be just how that primer behaves at normal pressures that are somewhere between a starting load and max. Reading primers alone - without any other information at all - is not reliable evidence that you are or are not in an unsafe place.
I think we are on the same page. A moderately flat primer on a commercial round with no other indicators... may be normal for that round/primer.

But are you saying that if your commercial round primer looked like the round on the left before firing and the round on the right after, without any other outward signs of over pressure, you would think it was normal? (Not my pic just one I found to illustrate a very flat primer)
flat-primer.jpg
The right had one scares me. I know its not one of my reloads but I would probably not fire any more of those rounds in my rifle.


Yes, you will see differences in primer with increased loads - I didn't say you should not. But what you are describing is normal and may simply be a sign of increased pressure, not necessarily overpressure.
I think we are in agreement here too, but I would stop my load progression if I saw the right primer above as I approached the listed max load even of there were no other signs.


It almost seems to me that you want to figure out a way to say "once my primer starts looking like a typical commercial primer I want to run that load over my chrony and let the FPS # it displays dictate if I should stop or keep going". That isn't going to work no matter how many times you rephrase the question. I may be off, but that's how I would best summarize how I read it.
I think I’m asking the opposite... I add MV as a data point in addition to watching other pressure signs...and I reach the the max load MV (or the commercial round MV) before any visible pressure signs, should I take the MV as an indicator and stop my testing? Or do I continue to increase the charge until I “see” pressure signs, or hit max load? Realize that before I had a chrono this is exactly what I would do since I had no other indicators.


But in general, not sure why -10% from max would be better than the published starting load - to me that sounds like trust one number, not the other. You wouldn't reverse that and say starting load +10% is max load....But it might be a thing that's common.
Hodgdon load data for .308 WIN with 150gr bullet on top of CFE223:
Max load: 51.5gr
Starting load: 48.4gr
90% of Max (51.5) = 46.3gr

Notice that the starting load is above the 90% of Max load. My mistake was to follow the rule, “Never go below the suggested starting load”. That and I should have referenced multiple load tables and gone with something closer to the low end. My mistake was assuming the powder maker would know better than load manuals.
48.5gr (starting load) = resulted in stiff extraction.
48.9gr (2nd step of ladder) = case stuck in chamber. Stopped shooting.

Lesson learned, if starting load is NOT lower than 90%.. go with 90% of Max even if lower than suggested starting load.
 
What did your case gauge say about the resized brass?
My Lyman case gauge said many of the Lee FL resized once-fired range brass cases were LARGER than SAAMI minimum spec. Some (about 1/3) of the cases did not fit all the way into the case gauge. A large portion of these resized cases would NOT chamber and allow the bolt to fully close on my rifle. I even tried rotating the cases 90deg and running them thru the resizing die a second time, it helped a few cases but not all.

When resized with the RCBS small base dies ALL cases fit into the case gauge and ALL chamber easily in the rifle. Sort of expected this since the small base die sizes the cases smaller than SAAMI so they cycle smoothly in semi/full-autos.

When I take case measurements at the critical points around the case, all Lee resized cases are smaller (by at least 0.002”) than SAAMI spec, even though they won’t fully fit into the case gauge or chamber. It could be the center of the case body is larger than normal but there is no spec to measure this diameter.

I took a fire formed once-fired commercial case (fired in my rifle):
- It does not fit into the case gauge
- The neck and shoulder diameter exceeds SAAMI; other case dimensions are less than or the same as SAAMI
- The case WILL fit into the chamber and the bolt will close (slightly stiff)
Using a headspace gauge, I measured the fire formed case and compared to ALL resized cases. All resized cases were at least 0.002-0.007” shorter in the headspace length meaning (headspce wise) they should fit anywhere the fire formed case fit.

I compared the Lee sized cases with the fire formed case... all standard dimensions are smaller but the Lee case will not chamber/close bolt. I cannot find a case dimension that exceeds SAAMI but the case will still not chamber. I don’t understand WHY the Lee resized cases do not chamber. My impression is that my rifle has a particularly small chamber (smaller than SAAMI spec) and any cases that are right at the minimum SAAMI size will not fit.

I sort of gave up. I resized ALL my once-fired range brass using the RCBS die. Manually cycled them thru my rifle chamber and confirmed the bolt will close on all. Once they are fired they will be fire formed and I will mostly neck-size them going forward.
The Lee die is back from being re-worked. They said they made it to the minimum spec/size. I’ll try it when I get some new range brass to resize.
 
Status
Not open for further replies.
Back
Top