What's a "good" variation in FPS?

[dmftoy1]

Ok, my first Chrono arrived this week and I've set it up and played with it. What do you consider to be a good high/low difference in FPS for handloads on a progressive press?

I had a batch of .500 S&W that I loaded on a single stage and dropped charges with a Lyman Model 55 powder measure and it was all over the place. I suspect this is because I contaminated my primers but I'm not sure.

On the other hand I had a bunch of .45acp that was staying within 10-15 fps over 10 shots with shots 11 and 12 being outside that range by another 10 fps or so. (higher an lower). I was pretty tickled.

Anyway, just curious as to what variation you see in FPS and what you consider 'good'. (as in your reloading correctly with your progressive press)

Have a good one,
Dave

 

[halvey]

You are good on your .45's. You should see about the same on the .500.

 

[Joey2]

How you benchrest will determine your FPS. If your weapon is in a vice verse hand held the FPS will change. If you fire your weapon from the free hand position you will get a varience also.

I may be wrong, but I found that free hand recoil will give you a lesser FPS than have the weapon in a vice.

 

[P95Carry]

Shooting position/method might affect fps but - if using a consistent method then variations should be fairly constant.... within that approach.

I think one thing to bear in mind - with a revo - X Frame here I assume, as you mention .500 ... is that cylinder variations can affect things from shot #1 thru shot #6. If loads are really carefully done then - if discrepancies seem large (+/- 25fps let's say, and worse) ........ I'd suggest you mic' up your cylinders and throats ... index one chamber and note speed for each thereafter - see if any correlation.

Revo's can introduce quite a measure of variation IMO - outside of the load accuracy factors.

 

[The Bushmaster]

"0" is what you are striving for. You'll never make it and it's frustrating. I can load 50 rounds exactly the same and still get around 50 t0 5 fps between sets of 5. Have fun. What you are looking for is near or at the velosity that you would expect of that round and that it is accurate. The difference between the fastest and the slowest has little to do with the ability of the round to preform unless you are experiencing a large difference and I mean 100 fps or more between fastest and slowest in a string..

 

[antsi]

the best measure of consistency...

...is the standard deviation. The high-low spread can be misleading, and it is also a poor indicator of how your process can be improved.

Many chronos will calculate the SD for you, but it can also be calculated by hand. You need to shoot enough shots to get a representative distribution (at least 10, say).

If you have a low SD, you know your process is generally good. Most of your individual velocity numbers will be within two standard deviations of the mean. For example, if the mean velocity is 1000 fps and the SD is 100 fps, the vast majority of your shots will be between 800 and 1200 fps. If you get a shot that is more than three SD away from the mean, that is a very unusual outlier and means you had one cartridge that was a real screw-up (in the above example, that would be one above 1300 or less than 700).

To compare two different loads, especially if the mean velocity is different, it may be helpful to divide the SD by the mean. That would show the difference between a string with a mean of 1000 and an SD of 100 (10/1000 = 0.1), versus a string with a mean of 900 fps and an SD of 250 (250/900 = .278). You want this dividend to be as small as possible.

 

[dmftoy1]

Thanks guys. I ran some more loads over it and the SD of my .45 loads is 12fps . ..I'm pretty happy with those accuracy wise but was surprised that they were moving faster than I would've thought.

My X-Frame S&W Model 500 loads are absolutely horrible though. My SD is 225.someting. I had some going off at 600fps and some going off at 1364 fps with the consistent one's right around 1200fps (which is what I was shooting for). I think I just did a really crappy job of loading them as it was my first reloading experience in 17 years and I was doing it with equipment that I wasn't completely familiar with. I also think I might hvae contaminated my primers slightly. I loaded up a new batch last night on the dillon and I'll have to give them a try when I get back from my trip.

Thanks again,
Dave

 

[griz]

That sounds like too big a spread for the 500. I've never used that round but 600 FPS is getting slow enough to risk stuck bullets for jacketd loads. I would do some checking to make sure I wasn't getting partial charges from a progressive set up. Isn't 1200 a light load for the 500? Is that from a reduced load of slow powder? Again I have no experience with this round, just looking for the problem.

 

[dmftoy1]

Well the batch that has the crappy results weren't loaded on the progressive, but rather a single stage with a powder measure I was using for the first time. I did weight the charges about every 10th round, but I suspect that my technique was what screwed things up. This "new" batch was loaded on the dillon and I'm very comfortable with that powder measure. (I was also checking about every 5th round just to be sure).

1200 fps is a "low" round for the 500. I'm about 1/2-1 grain below the suggested starting load. (but I have talked to people who are loading much lower than I am. (down around 1000fps). The case has enough powder in it with my loads that a double charge would overflow.

Have a good one,
Dave

 

[Nortonics]

Here's some handloads I did a while back - I was impressed with my abilities on these:

GROUP #4 - Handloaded 9mm Luger - Remington JHP 115 gr., Hodgdon Titegroup 4.5 gr. from a 3-1/2" Smith & Wesson 908S:
1)1113.0 1.2f
2)1112.0 0.2
3)1112.0 0.2
4)1112.0 0.2
5)1111.0 -0.8
6)1111.0 -0.8
7)1112.0 0.2
8)1111.0 -0.8
9)1112.0 0.2
10)1113.0 1.2f
High: 1113.0
Low: 1111.0
E.S.: 2.0
Ave.: 1111.8
S.D.: 0.6
95%: ±0.0

GROUP #5 - Handloaded 9mm Luger - Remington JHP 115 gr., Alliant Unique 5.6 gr. from a 3-1/2" Smith & Wesson 908S:
1)1113.0 0.0
2)1113.0 0.0
3)1114.0 1.0f
4)1113.0 0.0
5)1113.0 0.0
6)1113.0 0.0
7)1112.0 -1.0f
8)1113.0 0.0
9)1112.0 -1.0f
10)1114.0 1.0f
High: 1114.0
Low: 1112.0
E.S.: 2.0
Ave.: 1113.0
S.D.: 0.6
95%: ±0.0

GROUP #8 - Handloaded .357 magnum - Hornady HP/XTP 158 gr., Hodgdon Titegroup 6.1 gr. from a 4" Ruger GP-100:
1)1110.0 -1.2
2)1111.0 -0.2
3)1110.0 -1.2
4)1113.0 1.8
5)1113.0 1.8
6)1113.0 1.8
7)1108.0 -3.2f
8)1115.0 3.8f
9)1110.0 -1.2
10)1110.0 -1.2
High: 1115.0
Low: 1108.0
E.S.: 7.0
Ave.: 1111.2
S.D.: 2.0
95%: ±2.0

GROUP #11 - Handloaded .44 magnum - Winchester Jacketed HSP 240gr., Alliant 2400 16.5 gr. from a 5-1/2" Ruger Bisley Vaquero:
1)1108.0 -0.6
2)1108.0 -0.6
3)1109.0 0.4
4)1109.0 0.4
5)1109.0 0.4
6)1107.0 -1.6f
7)1110.0 1.4f
8)1109.0 0.4
9)1109.0 0.4
10)1109.0 0.4
High: 1110.0
Low: 1107.0
E.S.: 3.0
Ave.: 1108.6
S.D.: 0.8
95%: ±1.0

 

[griz]

Let us know how those rounds do. My question about the reduced load was because I don't even know which powders are used in the 500. I go to a faster powder for reduced loads in 44 mag, but a grain under the starting load sounds reasonable.

 

[fecmech]

Nortronics--I have been loading handgun rounds for over 35 years and chronograping for close to 30 years and I have never had any load with a 2 or 3 fps extream spread for 10 rounds! I'm not saying it can't happen but it has never happened for me. My good handgun loads and by good I mean those that stay under a 3" group size at 50 yds mostly average 20-30fps exteam spread with single digit sd's for 10 shot strings. I just chrono'd some ww factory 147's yesterday and they were 1017 avg., high 1031, low 1004, es 27 fps and sd of 8fps. My notes from years ago on ww and remington factory .38 wadcutter target ammo show approx 30fps extream spread for numerous 10 shot groups fired at the time. I've always felt if the extream spread was 30-40 fps for a 10 shot string it was a pretty uniform load, my $.02 Nick

 

[Nortonics]

I hear ya Fec, those were the impressive handloads - the others I did at that time certainly weren't close to these. Check my whole thread on these, as well as my chrono setup (with pics) in this thread over on handloads.com:

Lots-O-stuff brewin’ for tomorrow!

 

[Peter M. Eick]

Glancing over my excel database on loads, I note that I tend to be happy if the SD is under 10 on a 20 shot string and if the extreme spread is less then 30 for the same 20 shot strings I tend to be happy.

I have noticed that it is very gun dependent though!

 

[taliv]

shot a 5-shot group of Fed GM Match .308 today and got

2698
2724
2722
2709
2696

avg 2709, ES 28, SD 12

and my handloads

2572
2565
2577
2570
2574

avg 2571, ES 12, SD 4

that's pretty typical i think

 

[Mikul]

For pistol, I'm thrilled if my ES is around 10, but anything under 20 is good for 5 shots. Getting under 5 is amazing.

 

[griz]

Hello Nortronics,
I looked at your write up on the other site and am still puzzled by the near perfect velocities you are getting on some loads. I sure don't know how to account for it, but it seems impossible. Groups 7 and 8 are same cal, powder, and gun, differing only in bullet and charge weight. Yet one has an extreme spread of 245 while the other has an ES of 7. The strangest is group 6:

GROUP #6 - Handloaded 45 Colt - Meister 250 gr. RNFP, Alliant Unique 7.1 gr. from a 5-1/2" Uberti 1873 Cattleman:
1)1109.0 100.2
2)1109.0 100.2
3) 485.2 -523.6f
4) 867.4 -141.4
5)1109.0 100.2
6)1110.0 101.2
7)1110.0 101.2
8)1109.0 100.2
9)1109.0 100.2
10)1110.0 101.2
11) 870.6 -138.2
High: 1110.0
Low: 485.2
E.S.: 624.8
Ave.: 1008.8
S.D.: 198.4
95%: ±133.0

I don't think it's possible for a load to have eight shots within one FPS of each other and three shots off by several hundred FPS.

I'm not trying to challenge your credibility at all, I just think something is flaky with your chrono readings themselves. But I also have no idea what it is. The symptoms I see are the "bad" readings always seem low, and on the super consistent loads there seem to be a lot of readings that are consecutive repeats. But that last might mean nothing because I've never seen ES's that low and it might just be the way the distribution works out for super low spreads.

Again I'm not trying to insult you here, just saying it looks like something I can't explain is wrong.

And I'm glad you like your Bi-quero. I have one much like it. I use Titegroup for powder puff loads and Universal for all arounders, almost all lead bullets.

PS, What is the number behind the individual velocities? It appears to be related to consistency but sometimes has the letter F added.

 

[Mal H]

I had some going off at 600fps and some going off at 1364 fps with the consistent one's right around 1200fps

As has been said, that is way too much variation. I don't know if it's been mentioned above, but be sure you aren't too close to your chrono screens when you shoot that blaster. You may be tripping the start switch with the blast of gas from your .500 and the bullet itself trips the stop. That will give you a very low false velocity reading. I've seen that happen with a .44 Mag with a heavy load. You should be a minimum of 10 to 15 feet from the screens. When companies say "muzzle velocity", they don't really mean inches away from the muzzle, but within a few yards of the muzzle.

 

[Nortonics]

Hey Griz, I hear ya loud & clear about the flakiness that you speak of - it's there, and you're the only one to comment on it so far. The problem you're seeing is actually quite simple, and it has everything to do with how far away the screens were from my shooting platform. As I went up in caliber, so did the powder blast. The weirdness you see is from the powder blast reaching the first screen before the bullet, and that's what you get for a reading. Powder charge hits the first screen and starts the timer while the bullet passes the rear screen to stop the timer, and thus a VERY slow looking bullet on the chrono. I mentioned this weirdness in my original post about thinking I'd never shot a bullet at such low velocities - they weren't slow, I just had the chrono screens too close for the bigger calibers. Especially look at group 9 - do you possibly think 19 grains of 2400 behind 180 grains of lead would yield a velocity of between 300 and 600 fps? Of course it wouldn't. You can actually see a few loads that registered correctly between the bad ones - your picked group is a perfect example - shots 3 4 and 11 all had the powder blast trigger the first screen before the bullet reached it.

The negative or positive number after the velocity is the fps away from the calculated average of all shots in the group. The f indicates what the computer thinks is a flyer, or out of range.

Yeah, tell me all about it with the two entirely different powders and achieving those results. I can't explain how I've done so well, but I can tell you that I do read a lot, experiment a lot, and generally understand how to make an excellent load for a particular gun using whatever combination of bullets, powder, primers and shells. I've even been known to trim handgun brass, separate by headstamp and brass weight, even trim flash holes for Gods sake - the experimental days you know...

But I do swear those are all 100% legitimate loads that I made and chronoed and the results come directly from the CED...

Here's some of what I expect for accuracy. Although I haven't chronoed these loads yet I would expect something similar to what's above:

 

[DBR]

Nortonics:

Just a WAG, but I notice that the hyper consistant readings you got are near the speed of sound. I wonder if your chrono was seeing the sonic wave from the muzzle blast rather than the bullet?

 

[zeke]

Am more concerned with demonstrated accuracy of a load, than getting smallest possible variation of velocity. While certainly a good indication of possible accuracy or something amiss in handloading, just using the velocity difference may not give the accuracy ya want.

 

[Nortonics]

DBR wrote: Just a WAG, but I notice that the hyper consistant readings you got are near the speed of sound. I wonder if your chrono was seeing the sonic wave from the muzzle blast rather than the bullet?

Interesting observation. I would tend to think this wouldn't matter though as the collector screens are optically controlled - they're made with photo transistors that measure between an on and off condition only - light or no light, or in my case infrared light or no infrared light. They actually measure the shadow of the bullet passing by, or anything else that blocks that light beam for any reason, including a denser cloud of powder blast. I can also report further that the powder blast was evident, especially once I got to group 9 with the 180 gran .44 mags. It was after that group that I determined something was wrong and moved the screens back another 3 feet. This definitely helped, but they should have gone back even further as even a few more subsequent shots still powder blasted the triggering screen. With that alone I learned that the larger calibers require the screens back at least 20 feet from the shooting platform - high power rifles would require probably double that I'd imagine...

 

[larryw]

Let me throw in a couple thoughts along an entirely different line.

1. Large case, small charge, try tapping the butt of the blaster against the bench a couple times between shots to settle the powder against the flash hole.

2. Neck tension and crimp. Is your crimp as expected? That will affect combustion and pressure. Do you have a handful of tired brass that isn't grabbing the bullet with enough tension to keep the bullet from jumping prior to proper pressure build?

Trust me, look at these two things: Been there done that.