Lots of 9mm testing in 2 barrel lengths

S

Shadow9mm

New member
So I went and shot a bunch of stuff over the chronograph today. I changed the way I am keeping my data and wanted good data for my individual guns and was curious to see the differences in barrel length. Hope you find this interesting and or helpful.

Note, The listed velocity from speer for the #7 load was 1180fps at 9.0g, however I met that velocity at 8.4g. I will be using 8.4g as it should be duplicating the proper pressure as it created the same velocity. I did experience some primer flattening and cratering at 8.8 and 9.0g and velocities were above listed. I called speer and they seemed to thing i was due to using different brand brass and primers than listed in the manual. it was intermittent and seemed to very with head stamp. Also my first time using fiocchi primers, not sure if they are softer than average.

Almost forgot Chronograph was set out at about 9ft. 5 rounds per test group. I considered including SD/ES, but its already a bit busy for my taste.

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AA-7 is my go to powder for full house loads in 124 and 147 gn 9mm.

Am using a Fed small mag pistol primer with reduced charge, but also keeping the velocity's down to 1180 fps in 124 gn. For my use the mag primer gave better accuracy (back when i could see better)
 
zeke said:
AA-7 is my go to powder for full house loads in 124 and 147 gn 9mm.

Am using a Fed small mag pistol primer with reduced charge, but also keeping the velocity's down to 1180 fps in 124 gn. For my use the mag primer gave better accuracy (back when i could see better)
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unfortunately I don't have any small pistol magnums. I have standard small pistol, and standard small rifle. my handguns will set off small rifle. however SD/ES were reasonable in 1 loading.

8.6g
G19 avg 1212, SD 11.55, ES 23
P365 avg 1145, SD 6.24, ES 15

considering the consistency I think that is where I am going to be looking. the 8.8 and 9.0 were the ones that seemed a little extra stout.
 
I think you are making a basic error assuming you should be getting essentially identical results when you are not using the same identical components (including test guns!).

Eveybody's data was tested in THEIR GUN, not your gun, and their gun is not your gun. Similar results are usual, but drastically different results are not an impossibility, and often not uncommon.

and what does it really matter, anyway? IF you're getting 30-50fps difference from what they got? Even 100fps difference isn't much in real terms. Yes, its calculatable, and yes there is a difference but when you get to terminal bullet performance how much difference do you think a handful of fps or Ft/lbs matters??

Sure, velocity matters, bullet drop at range, but consider this, with "regular" .30 cal rifle bullets a 100fps difference in velocity means about 1/2" difference in drop, at 100 yds.

IF you are capable of correcting for one given amount of drop, you are capable of correcting for any given amount of drop. Its all just a matter of knowing how much you need to adjust for.
 
Thing is, the variance, even with the same barrel length has been down, or lower than listed. Im my years of reloading I can only remember seeing higher once, and it was very hot that day. Velocities came back to below published in cooler weathet. However my testing yesterday was at 70F. And i am not familiar with the temperature stability of aa#7.

So the question then becomes, how much variance is normal. 60fps is 5% above listed at max in this case.
 
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The velocity measurement is not an absolute pressure measure, but the best tool most of us have available. Comparing the recorded velocity's with the expected velocities, is a tool to take into account the variances in primer's, bullets etc. Certainly there are inaccuracies using velocity's in this manner. However when developing loads near the top of the data, imo it provides a useful safety factor. Certainly some can, and do disagree. For my purposes, 100 fps over top expected data in 9mm matters.

Am not experienced in AA-7's temp/velocity variations, but it is a very useful lower flash powder. The only real problem have experienced with it is the large granules left over can get blown back into the action when using certain muzzle accessories. If the firearm's action is tightly fitted, it can cause a problem.
 
zeke said:
The velocity measurement is not an absolute pressure measure, but the best tool most of us have available. Comparing the recorded velocity's with the expected velocities, is a tool to take into account the variances in primer's, bullets etc. Certainly there are inaccuracies using velocity's in this manner. However when developing loads near the top of the data, imo it provides a useful safety factor. Certainly some can, and do disagree. For my purposes, 100 fps over top expected data in 9mm matters.

Am not experienced in AA-7's temp/velocity variations, but it is a very useful lower flash powder. The only real problem have experienced with it is the large granules left over can get blown back into the action when using certain muzzle accessories. If the firearm's action is tightly fitted, it can cause a problem.
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Very insightful, thank you. I was only 60fps over, but thats still more than i expected. And thay felt more stout comparitively, than the others. Down a quick rabbit trail I believe i know the certain muzzle accessories you are speaking of. I am planning to get some next year. Are there any powders i should avoid? Or any i should look into to help things run smoothly?
 
Shadow9mm said:
Very insightful, thank you. I was only 60fps over, but thats still more than i expected. And thay felt more stout comparitively, than the others. Down a quick rabbit trail I believe i know the certain muzzle accessories you are speaking of. I am planning to get some next year. Are there any powders i should avoid? Or any i should look into to help things run smoothly?
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Very generally speaking the faster powders may burn cleaner and less noise than the slower ones. Smaller calibers are easier than larger ones. Subsonic is much quieter, especially in a smaller caliber gas operated action where you have the ability to keep the gas from opening the action.

AA7 leaves particles that can spit back at you, but provides max/close to max velocity in 147 gn 9mm, while being sub sonic. V V powders burn much cleaner, maybe a little less velocity, although a lot of people push V V more than i like for my purposes.

There are undoubtedly lots of alternatives, but am not an exspurt and not experimenting as much at this stage of life.

The mention of 100 fps was a response to "Even 100fps difference isn't much in real terms". Just a polite difference of opinion or purpose. Another warning sign i take seriously is when the velocity's stop increasing as much when more powder is added. Some like and strive for a min ES/SD, but it can also be a sign of higher pressure, in addition to consistency. Again, it's just an opinion.

Sorry lost my manners, you're welcome.
 
especially in a smaller caliber gas operated action where you have the ability to keep the gas from opening the action.
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This part has me confused....

If you have the ability to keep the gas from opening the action, then its NOT a gas operated action.

The velocity measurement is not an absolute pressure measure, but the best tool most of us have available. Comparing the recorded velocity's with the expected velocities, is a tool to take into account the variances in primer's, bullets etc. Certainly there are inaccuracies using velocity's in this manner. However when developing loads near the top of the data, imo it provides a useful safety factor. Certainly some can, and do disagree. For my purposes, 100 fps over top expected data in 9mm matters.
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I agree, but I need to point out that while getting higher than expected velocity results does matter, in the sense that it is something to be aware of, and pay attention to, it does not automatically mean danger. It might, but then again, it might not. And that will be determined by the gun you are shooting, not anyone else's test with a different gun.

While we expect, and usually get very similar results, one must always remember that each individual combination of gun and load can be a law unto itself, and things at both the high and low end of the bell curve DO happen.

Here is an example I personally experienced. It is an example of the principle, and won't be directly applicable beyond illustrating that.

.357 Magnum, 125gr JHP bullet 2400 powder. Load taken from the Speer manual. Speer's test gun was a 6" Ruger Security Six. Speer's data said the load was 1555fps.

I shot the load from a S&W M19 6", a S&W M28 6", and a Desert Eagle 6".

The model 19 clocked 1620fps and the load was TOO HOT! Cases could NOT be extracted and ejected by hand pressure, a rod and small hammer were needed to drive them out of the cylinder. Too HOT, for THAT gun!

The Model 28 clocked 1670fps, 50fps faster than the model 19, and 120fps faster than the Speer book listing. Cases extracted and ejected with normal hand pressure.

The Desert Eagle (with a nominal 6" barrel) clocked 1720fps, and funtion was flawless.

ALL three guns gave velocities well ABOVE what the Speer manual showed. The load was unsuitable (but NOT unsafe) in ONE of the guns and fine in the other two.

I fully expect that, had I tested different guns, or even different examples of the guns I did use, I would have gotten slightly different results. It is entirely possible that different guns tested with that same ammo could have turned in velocities lower than the Speer book value.

This PRINCIPLE applies to your 9mms and indeed, every other gun/ammo combination out there.

Chronographs can be the "stairway to heaven" but they can also be the "boulevard of broken dreams".

IF you expect to get exactly what they got, you will probably be disappointed at some point. If you expect close, but understand it can be different, you're on the right track.
 
I think he means an adjustable gas block with a cut of setting for use with certain muzzle attachments.

I use the chrono for handguns so i can measure the velocity increases while working loads up as well as a rough gauge of if it is performing as intended.
 
Here's where some of the roughness of the idea comes from:

Shadow9mm said:
I will be using 8.4g as it should be duplicating the proper pressure as it created the same velocity.
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When you match velocity, you have matched the average pressure accelerating the bullet during its travel down the whole length of the bore. You have not, however, matched the peak pressure, which is the one we concern ourselves with. In general, if the barrel and chamber have the same dimensions as the load whose velocity you are trying to match, your peak pressure is actually higher when you find less powder matches the published velocity and lower when you need more powder to match the published velocity. This is because less powder makes less total gas, so pressure drops more near the muzzle, and you get less acceleration near the muzzle. That loss of late-barrel acceleration has been made up for by higher pressure and acceleration at the peak. The reverse is true when you need more powder to achieve the same velocity. There you get some extra late-barrel acceleration due to the higher gas volume raising late-barrel, and muzzle pressure, so less acceleration has to come from the peak pressure. If the difference in powder required is due entirely to smaller case volume, with Accurate Number 7 and the Speer 124 grain Gold Dot, a velocity match will occur in the smaller case when the peak pressure is about 13 times higher than when the case volume is large enough for 9 grains of powder to be needed to reach that same velocity.

However, all this can be turned on its head if the powder in the 9-grain data load is not burning very completely in the bore and the reduction in powder charge is caused not by powder space change but by your lot having a faster burn rate than the data lot did. In that scenario, the faster burn rate is improving the percent of powder burned completely in the bore and the resulting efficiency increase can actually make more gas while the bullet is still in the bore, and thus be responsible for peak pressure actually going down slightly.

I know. It's a headache. The bottom line, though, is that you can't really know peak pressure very precisely from velocity alone. That 13% difference in same-velocity loads isn't unusual, particularly because of powder and component variation. SAAMI has some examples from labs testing pressure on the same lot of reference ammunition, and even then copper crushers got readings different by over 20% and piezoelectric transducers disagreed by over 10%. If you get the impression peak pressure isn't really very exactly controlled in firearms in general, that's the truth.

Note that the above also assumes identical test conditions.

Shadow9mm said:
Chronograph was set out at about 9ft. 5 rounds per test group.
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Published commercial ammunition specifications, unless stated otherwise, and most all published load development, also unless stated otherwise, uses the SAAMI standard, which has the midpoint of the chronograph at 15 feet from the muzzle and always fires a 10-round sample, always makes sure the powder has fallen back over the flash hole before firing each shot, and fires them only after conditioning them to be at a temperature range of 60°F-80°F. 1–3 fouling shots are fired through the clean barrel before firing the 10 shots for the sample record. The barrel is cleaned and all that repeated for the next sample.

If your data collection adhered to the SAAMI standard, the velocity error in comparison to a published number from using 9-foot chronograph spacing instead of 15-foot chronograph spacing for the 124-grain Gold Dot loads will range from 16 fps at the lowest velocity to 20 fps at the highest velocity if you were shooting in standard atmospheric conditions at the time you fired them.

With a 5-shot sample instead of a 10-shot sample, the variance is expected to be 2.1 times greater, on average.

I know all that's complicated, but even if you don't take an interest in trying to duplicate testing to SAAMI standards, at least you are aware if where some of the differences lie.
 
Thank you Unclenick! That was very informative. I did not know 15ft was the saami spec for chronograph. I have always used 15 feet for rifles, but 9ft for pistols as it was easier to do.

I was short on some of bullets and ammo for testing. And I felt wasteful shooting more than 5 as it was, went through 150rnds.
 
Yes. Testing can get really expensive really quickly. And mostly, with handguns, you are looking at things like, does it function in the gun? Is it at a target or combat velocity range or making a power factor needed for a match? Is it as accurate as the intended target requires? And you can, as I did, run a ballistics program to find the 15-foot velocities from a 9-foot velocity.
 
Shadow9mm said:
I think he means an adjustable gas block with a cut of setting for use with certain muzzle attachments.

I use the chrono for handguns so i can measure the velocity increases while working loads up as well as a rough gauge of if it is performing as intended.
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This. Am in possession of gas various gas operated firearms with this capability. So it is not theoretical or read from a publication somewhere, but an actually observed fact.
 
44 AMP said:
I agree, but I need to point out that while getting higher than expected velocity results does matter, in the sense that it is something to be aware of, and pay attention to, it does not automatically mean danger. It might, but then again, it might not. And that will be determined by the gun you are shooting, not anyone else's test with a different gun.

While we expect, and usually get very similar results, one must always remember that each individual combination of gun and load can be a law unto itself, and things at both the high and low end of the bell curve DO happen. ]

Looks like we agree, and never intended to imply some king of absoluteness. Am using the tools and data available, and not making every reloading project a research paper.
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If you have the ability to keep the gas from opening the action, then its NOT a gas operated action.
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My apologies for not being specific enough. Point being that If you have the ability to keep the gas from opening the action, and you use it, then its NOT a gas operated action.

When you shut the gas off, the gun becomes a manually operated repeater, it is no longer gas operated, until you turn the gas back on, again.

The M14 (and M1A) have a gas spindle specifically to shut off the gas and turn the rifle into a manual action, for grenade launching.

The Wildey pistol has an adjustable gas system, which includes a "0" setting, (off) and when so set must be operated manually. The thought of an AR pistol with an adjustable gas block which has an off setting had not occurred to me, but now that it does, it would be in the same group.
 
44 AMP said:
My apologies for not being specific enough. Point being that If you have the ability to keep the gas from opening the action, and you use it, then its NOT a gas operated action.

When you shut the gas off, the gun becomes a manually operated repeater, it is no longer gas operated, until you turn the gas back on, again.

The M14 (and M1A) have a gas spindle specifically to shut off the gas and turn the rifle into a manual action, for grenade launching.

The Wildey pistol has an adjustable gas system, which includes a "0" setting, (off) and when so set must be operated manually. The thought of an AR pistol with an adjustable gas block which has an off setting had not occurred to me, but now that it does, it would be in the same group.
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Not a problem, and maybe just semantics? Occasionally my use of the english language is poor, usually it's really bad.
 
Whats the difference between that and a manually operated repeater?
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A straight pull bolt action IS a manually operated repeater. A semi with the gas shut off still has a spring to close it, but it requires the action be opened BY HAND, and does nothing until you do that, so that makes it a manually operated repeater.

The nice thing about a gas system that you can shut off is that you can turn it on again when you want.

A firearm with a non-adjustable (or one without an "off" setting) gas system CAN become clogged, and that turns the gun into a manually operated repeater, until the system is cleared and that can take more than just a bit of work.

I knew of one fellow who "knew more than the factory" and clogged the gas system of his Desert Eagle by shooting lead bullets, something the owner's manual (and numerous other sources) say not to do.

Local smith could not clear it. Gun went back to the maker, and they refused to try. Not a repair covered under warranty. They installed a new barrel assy, and returned the gun along with the bill for the barrel. $283 at the time when the new gun cost $600.
 
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