Using a Chronograph, how to use it and what dose it mean?

Status
Not open for further replies.

Wildbillz

Member
Joined
Apr 10, 2010
Messages
1,014
Hi All
So I got this Chronograph so I could know what's going on with my reloads. Its a CED M2. I took it to the range and got it all setup. Started shooting across it and found my velocity's were way lower then I expected.

So first question; How do I know if the Chronograph is reading true?

I first fired a five shots of surplus 308Win (CAVIAM) I was expecting to see about 2700 fps, maybe a little less as the rifle only has a 18" barrel (Savage 110 Scout rifle). My first shot came in at 2437 fps, average of all five shots was 2452 fps the highest being 2474 fps. After firing all my test loads and recording the info, I fired a last string of the control ammo and got an average of 2452 fps. Next time around I am going to get myself a few rounds of the LC that is available right now and see what sort of velocity's I get with that.

So was I expecting to much from the control ammo? How much difference would a longer barrel make, if any? Will the ambient temp make a difference in my velocity's?

Next I fired some 5.56mm (Malaysian) across it and an average of 2891 FPS. I was think it would be closer to 3000 fps? Then I shot some of the ammo I loaded (23grn of AA2230 with a USGI pull down 55grn Fmj) expecting 3000 fps per the spear manual and got readings in the 2500 range? from the manual they were using a 22" barrel and I only had a standard AR lenth one with a 1 in 9 twist.??

When I tried it on the pistol range I started to get a lot of errors messages on it. The sky had gone a bit over cast so I don't know if that was messing with me or not. But most of my pistol velocity's seems a little low also.

Any advice on how to use this thing and or what to make of the readings that I got?

Thanks
WB
 
Welcome to the reality of how fast things go vs how fast we think they will or are advertised.

While you can get an occasional bad reading due to sun, shade, angle, etc,
The sky had gone a bit over cast
, but most of the time the chrono is telling you the truth.

I had some of that Malaysian ammo and that sounds about right (Going from memory anyway.)

One of the first things many new chrono owners post is exactly that, "it was slower than I thought it was".

Pistol data done in pressure barrels often doesn't translate to real world guns well, especially with revolvers. That is one thing I like about the Speer manuals, they use a lot of real guns to get data.
 
To make it very simple speed sells and this holds true very often with both factory loaded ammo and listed velocities in loading manuals. Estimating velocity from data printed in manuals will almost never represent what your firearms are doing in reality. Also there will be some variation between two identical rifles referred to as fast or slow barrels...and yes ambient temperature will cause varying results along with differences in primer selection, elevation and clean or dirty barrels....so so so many variables
 
A lot of small factors are adding up I believe. For one thing a lot of factory ammo is slower than advertised, some by 100 fps or more.

You will see some decrease in velocity with shorter barrels. Most 308 loads are calculated in test barrels 24" in length. Expect 15-20 fps less for each inch, so that can easily account for 100-150 fps of the difference.

Temperature effects ammo speed. Roughly 1 fps slower for each 1 degree lower temperature. If the load was tested at 80 degrees, and you shoot it at 30 degrees that is another 50 fps.

Also test barrels have chambers and barrels cut to minimum standards which are a lot tighter than most factory barrels. This is why few factory barrels will match published speeds. This could easily account for 50-100 fps.

The last thing to consider is that no 2 guns are exactly the same. It is very common for different guns with equal barrel lengths to shoot 25-50 fps different. I've seen over 100 fps difference in one case between 2 rifles with equal barrel length and ammo from the same box.
 
Once I know the fps of a good round I can calculate the ballistic arc.

I like to use the optimum charge weight method to determine best load then calculate the arc.

Makes it easy to determine my real world point blank range for a hunting round.
 
Welcome to owning a chronograph! They are fun. The more you use it, the more you'll appreciate it, IMO.

Your CED M2 will tell you if the conditions are not allowing for a start or end signal from the sky screens. You'll get an error message on the LCD display.
 
What was probably most enlightening to me was seeing how a very stout 44 mag load of H110 was only 100fps faster than a comparatively mild load of 2400.
 
You have a very good chronograph, trust the reading.

So what does a chrony do for you?
- Firstly is gives your projectile speed, which is the closest approximation to chamber pressure you will get without strain gauges. So it is avaluable tool to stop you blowing yourself up with overpressure.
- It allows you to establish how good your loads are through the calculation of the standard deviation ( a statistical measure of repeatability / accuracy) of loads speeds.
- It allows you to now measure the more subtle changes in your reloading process. Magnum vs. normal primers, neck sizing vs. F/L sizing, cripming vs. no crimping ....... think you get the point.
- It allows you to duplicate a load when powder batches vary by targetting accuracy node speed.

Do not shoot to close over the sensors, apart from the obvious shooting the chrony readings tend to be more erratic (on my Chrony that is). I have the crosshairs about 10" higher than the sensors which in reality is only about 8.4" due to the scope barrel difference.

Always keep spare and fresh batteries. You can spend the week lovingly preparing your handloads only to get halfway through the shoot to have to chrony go bad on you. Been there got that T Shirt. I now power with a small 12V lead acid with appropriate voltage dropping circuit to get down to 9V for the chrony.

If you don't record your chrony results for later reference then a chrony becomes a little redundant.

Enjoy, one of the more useful reloading tools.

Cheers
 
Shooting the factory ammo as a control is a good starting point. It allows you to see what YOUR gun does with it under YOUR shooting conditions.

Many people like to duplicate factory loadings. You now have a reference velocity to aim for.

As the posters above have noted, published velocities for both factory ammo and reloading manuals are determined under very specialized conditions and will likely be higher than what you get out of your gun in the "real world."

I always stay within the published minimum and maximum charge weights, but I don't expect to get the same velocity they publish.

If your .308 likes the Lake City or the Federal Gold Medal Match or some other premium match ammo, use that velocity (you measured) as a control and a starting point for your handloads. With good case prep, quality components, and some experimentation you can tune the load to your rifle.

If you are shooting a modern bolt gun, you can probably get an accurate load which is a little hotter than LC. The mil-spec ammo is constrained to certain pressure curves so it will function (and not damage) the M14/M1A type service rifles. The Hornady reloading manual has separate sections for the 7.62 NATO (for the service rifle) and the .308 Winchester (for modern bolt action rifles). That may also be why your velocities for LC are lower than you might think.
 
Chronographs are interesting tools. Here's what I've observed in using them as well as what others have reported.

A given load in a given rifle will produce an average muzzle velocity different for several folks shooting it. I've seen as much as 50 fps and close to 100 fps has been reported by reputable sources. Us humans don't all hold the rifle against our bodies with the same pressure and recoil axis angle.

A given load that's very accurate across several rifles will produce an average muzzle velocity spreads of 50 fps or more across all of them. Their barrels' bore, groove, chamber and firing pin specs are a little different from each other as is how the rifle's held by each person.

There are people who do not work up a load when changing component lot numbers or barrels. Chronographing new loads' components with the same recipie will have different muzzle velocities, but accuracy is still 1/4 MOA at 200 yards. Sierra Bullets, for example, has been doing this for decades.

Loading to a given muzzle velocity does not mean it'll produce the best accuracy and the same pressure. Look at load data listing pressure and note that muzzle velocity does not go up and down with pressure. Some loads produce lower muzzle velocity and higher pressures for a given bullet than another load producing the opposite; higher velocities with lower pressure. Never ever equate muzzle velocity with pressure; they don't go hand in hand across all loads. And different powder lots in the same recipie will easily have a 50 fps spread as well as a few thousand PSI numbers.

Regarding "tuning" a load to ones rifle, note that if one shoots several groups with a load and there more than a 10% spread in their extreme spread, they're not shooting enough shots per group for any one them to be meaningful. The largest one best represents the accuracy level that can be counted on all the time. A composite of all fired groups aligned to the aiming point is larger than the biggest one shot.
 
Last edited:
I use my chrono to test handgun ammo so I can know if the velocity is high enough to reliably expand the bullets.

I use a chrono to test rifle ammo so I can reliably chart bullet drop and downrange performance.

I use a chrono to find out the true velocity of factory ammo so I can try to replicate that ammo with my reloads.

I use a chrono to be sure the loads I'm building aren't producing too much velocity which is probably a sigh they are overpressure.

I also own a chrono because I like toys!!! :p
 
Welcome to the world of chronographs. Yes you can and will see lots of different things that will make you scratch your head.
You'll find some loads such as you did that are way slow, and you'll find some loads that clock a good bit faster than what the data said it will.
But the only thing you can really take from it is that at that moment that's how fast your bullet went.
There are a ton of things that can vary the velocity from one load in different guns, from the guns chamber size to the difference in sizing done by the resizing die, neck tension etc.
Best way to check you chronograph is with some standard velocity 22 lr rounds from a rifle, those are pretty dang close to 1080 fps from most every rifle they get shot out of.
Keeping a fresh battery and setting the chronograph back 15- 20 feet from the muzzle will help keep the goofy readings down.
 
- Firstly is gives your projectile speed, which is the closest approximation to chamber pressure you will get without strain gauges. So it is avaluable tool to stop you blowing yourself up with overpressure.

Be careful with this concept. It works in one direction, but not in the other.

Good example: "Geez, when I load Power Pistol in 45ACP using the Hornady manual, I get velocities 200FPS faster than the manual says...I need to cut back and stay below the published max velocity to make sure that I'm not over pressure." This approach lets you avoid beating the hell out of your firearms and risking failures from overpressure.

Bad example: "Geez, my .308 loads are 200fps slower than the manual says they should be. I can probably go a few grains over max then, since clearly I'm getting lower pressure in my gun than they did when they did the testing." This approach will help you blow up your gun.

I can't imagine reloading without a chronograph. It is extremely helpful to have actual velocities to plug into ballistics calculators. It also lets me know if there are big differences in new component lots. There's no other way to know if your velocity is consistent.

Chronograph velocity is a poor approximation of chamber pressure, but it's about the only affordable way to estimate chamber velocity.

Best way to check you chronograph is with some standard velocity 22 lr rounds from a rifle, those are pretty dang close to 1080 fps from most every rifle they get shot out of.

Some people buy a brick of high quality target ammo that is really consistent, and they begin each chrono session with 10 rounds out of the .22 with the same lot of target ammo to verify that everything is reading correctly.

-J.
 
Best way to check you chronograph is with some standard velocity 22 lr rounds from a rifle, those are pretty dang close to 1080 fps from most every rifle they get shot out of.

Having chrono'd Eley, Federal, RWS, Olimp and Temp rimfire subsonic match ammo, it's all had velocities at 15 feet from 1020 to 1110 fps. Cheaper rimfire subsonic ammo's had a greater spread. And rarely does two rimfire barrels of the same length shoot a given lot number the same fps out the barrel. So, with a 90 fps spread across those subsonic rounds, that's about 8.4% spread about the 1065 fps average.

Which one would you want to use to test your chronograph thinking there all pretty dang close to 1080 fps?

SAAMI spec for standard velocity .22 rimfire's 1135 fps. For match ammo, 1100 fps in rifle and 1135 fps in pistol.
 
Last edited:
Which one would you want to use to test your chronograph thinking there all pretty dang close to 1080 fps?

I don't think that the absolute value is as important as consistency.

I agree, unless you have something with an absolutely reliable velocity, you'll never know how close your setup is to reality.

You could go full nerd and set up the chrony so you can drop a ball bearing through it and use Newtonian physics equations to check it. Gravity is pretty consistent everywhere. Actually, I'm going to do that with mine, now that I think about it!

You could always take your brick of .22 match ammo and your .22 rifle and shoot it over a couple of high-end chronographs to see how it compares.

-J.
 
Reporting back from nerd land...

My Chrony won't read under 30fps, so the drop would have to be from higher than what I can do indoors. I tried some from ceiling height and got error messages.

Also, when I point the chrony down, the weight of the skyscreens bends the first eye down a little, which will throw off the measurement.

I could set things up outside and rig a diffuser and drop stuff off the roof.

I don't care enough to do that, but you could.

-J.
 
Using a Chronograph

I am not an expert on the chronograph, but I have fired my 223 reloads in my 16 inch barreled AR 15 and get 2850-2800 fps then using a Ruger Model 77 Mark 2 with a 26 inch target barrel and same ammo would show 3150-3175fps. Barrel length will make a big difference in my case, but if you were shooting 16 inch barrel verses a 20 inch barrel you may not see much difference at all. I also had error message come up my first 3 shots over the chronograph on an overcast day and I took the diffusers off of the steel rods and then it never came up error again the rest of the day. I agree with the other posters that stated that if you are going to reload get a chronograph to check your loads, it will show you if you are getting a wide spread of velocities. If you do have a wide spread of velocities double check the steps in your loading process on the powder drop, I had one batch when I was working up a load with a different powder that had a larger spread than I thought was normal. I double checked all the settings and the Lee double disk powder drop was not moving far enough over the hole and causing erratic powder drops. Bottom line if you reload, invest in chronograph it is money well spent!! Also I marked my rods with tape about 3 to 4 inches from the top, that way if you are shooting with a scope or and AR with the iron sights you can use the tape as a guide not to shoot under so you don't kill your chronograph with a low round.
 
Not only do I shoot my reloads through mine, I also used it to measure the speed of my bow. got a nice 290pfs with my hunting arrows and broad heads. sometimes its nothing more than geewhiz stuff.
 
Having chrono'd Eley, Federal, RWS, Olimp and Temp rimfire subsonic match ammo, it's all had velocities at 15 feet from 1020 to 1110 fps. Cheaper rimfire subsonic ammo's had a greater spread. And rarely does two rimfire barrels of the same length shoot a given lot number the same fps out the barrel. So, with a 90 fps spread across those subsonic rounds, that's about 8.4% spread about the 1065 fps average.

Which one would you want to use to test your chronograph thinking there all pretty dang close to 1080 fps?

SAAMI spec for standard velocity .22 rimfire's 1135 fps. For match ammo, 1100 fps in rifle and 1135 fps in pistol.
I don't know where you got all those numbers but I don't think any of them are correct.

I have never seen a cartridge that will generate more velocity in a pistol than a rifle yet you quote 1,100 fps in a rifle and 1,135 fps from a pistol. Also, you don't give the bullet weight for your velocities which will change the velocity of each type of ammo. I'm not getting on your case, just trying to understand what you are posting.
 
I use my chrono to test handgun ammo so I can know if the velocity is high enough to reliably expand the bullets.

I use a chrono to test rifle ammo so I can reliably chart bullet drop and downrange performance.

I use a chrono to find out the true velocity of factory ammo so I can try to replicate that ammo with my reloads.

I use a chrono to be sure the loads I'm building aren't producing too much velocity which is probably a sigh they are overpressure.

I also own a chrono because I like toys!!! :p

This pretty much covers it for me. Well said.

I consider shooting factory ammunition over the chronograph as "calibrating" the firearm. i get an idea if the gun is fast or slow.

Here is an example of how different firearms can have vastly different velocity results with the same ammunition.

i have two AR-15 A2 rifles with 20" barrels. With my service rifle match loads, one shoots 200 fps faster than the other, about an 8% difference.
 
Lots of good advice on how to use a chrony and what it can tell you.

Now lets get back to your chrony readings.

I think they are low as well. According to Accurate and Quickload, your 23gr load with 55gr bullet should generate somewhere in the vicinity of 2800fps with an 18 inch barrel. Your chrony read this load at 2500fps. That is indeed low. Why is the big question.

How far did you have the chrony from the muzzle?

Did you have the sky screens installed and installed correctly?

Did you have it level to your shooting plane?

Did you have it straight as in diagram #1 found here?
http://thefiringline.com/forums/showthread.php?t=533443&page=3
 
steve4102

Lots of good advice on how to use a chrony and what it can tell you.

Now lets get back to your chrony readings.

I think they are low as well. According to Accurate and Quickload, your 23gr load with 55gr bullet should generate somewhere in the vicinity of 2800fps with an 18 inch barrel. Your chrony read this load at 2500fps. That is indeed low. Why is the big question.

How far did you have the chrony from the muzzle?

Did you have the sky screens installed and installed correctly?

Did you have it level to your shooting plane?

Did you have it straight as in diagram #1 found here?
http://thefiringline.com/forums/show...=533443&page=3

Hi Steve
Distance was about 15 feet. I tried moving it out to the max lenth of the cable at one point to see if it would help to eliminate the error message I was getting.

Installed correctly as far as I know?

Yep I used the little bubble and had it as level as I could.

Straight I had not thought of. That might have been part of the issue. I will have to check it out this week when I go out.

Thanks for the link. I will read through that this evening and see if I can gain any other info to help.

WB
 
Once I know the fps of a good round I can calculate the ballistic arc.

I like to use the optimum charge weight method to determine best load then calculate the arc.

Makes it easy to determine my real world point blank range for a hunting round.

I don't know why you need to chrono a load to get your real world point blank range, unless you just like doing that, which is certainly okay.
Just set a target up at where you want your point blank range to be and dial it in.
The stand I've been hunting has a maximum shot of about 200 yds, so I dialed it in at 2" high at 100, then took it back to 200 and fine tuned it. Simple as that.
 
ArchAngelCD, here's a link to a site showing a bunch of standard velocity ammo velocities from a bunch of rifles. All the rimfire match ammo had 40-grain bullets.

http://www.accuratereloading.com/22rf.html

And from SAAMI's web site, pages 8 and 9 in the following noting the velocity spreads mentioned for each standard velocity and match ammo:

http://www.saami.org/specifications_and_information/publications/download/208.pdf

And here's a site testing rimfire ammo in different barrel lengths and makes:

http://www.rimfireshooting.com/index.php?/topic/5118-a-local-barrel-length-vs-velocity-test/

Eley marks some of the match ammo with an average muzzle velocity obtained from 4 different barrels.

The man often testing rimfire match ammo at the US Olympic Training Center said there's easily a 50 fps spread of a given lot across a bunch of barrels.
 
Last edited:
Status
Not open for further replies.
Back
Top