9mm 115gr velocity and accuracy

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BigBob1

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I saw an old post about speed of sound velocity and if it matters on accuracy for handguns. The thread is closed so can't reply to it.

I think the person assumed since it affect pellet guns that it should affect heavier pistols even at 25 yards. I'm reloading 9mm and at stage 1 (just getting it consistent and not blowing anything up in the process) Now I'm wondering if fps makes much of a difference with 9mm 115gr.

I own Daystate PCPs and know they can be affected if you go too much past 900fps and agree with most of that thread that in theory it should make a difference But I saw a article on match vs regular 9mm and their results showed best accuracy in the (bad) transonic area of under 1180 fps at 25 yards which sort of bucks the posters theory of staying above 1210 fps for better accuracy.

Its putting the 115gr on the edge of too much power (for guns that are not p+) to get them above 1200 fps from a 4" barrel. And subsonic they don't have power.

It appears other factors outweigh any speed of sound issues for 115gr. It could be that the mass of 115gr vs a 16gr pellet is so great that even in the transonic region the air turbulence just does not have enough time to disrupt the bullet much in 25 yards. With a pellet gun and 16g pellet its so light that moving that small mass around by turbulence will have a noticeable effect.

Take a look at this test of match vs non match grade 9mm ammo and see that velocity at 1100-1200 range (which is suppose to be bad for turbulence) had great accuracy and better than some of the faster bullets (1200fps +)

These results are in stark contrast to that posters theory on accuracy and velocity. It might be a factor but it appears that one can load 9mm and not worry about if they are above the speed of sound for best accuracy.

Has anyone here found a correlation which says it matters?

bf8bc9d599.jpg
 
Looking at your chart their are no loads that have produced nail driving accuracy even shot from a Ransom rest. Every gun has it's own personality as far as what bullet and powder combo it likes best. My 9mm's like 124gr bullets better than 115gr bullets. All you can do is try different loads to see what gives you the best accuracy at what ever distance you shoot at. Most 9mm pistols are not target grade anyway so good luck in your quest for accuracy.
 
BigBob1 said:
9mm 115 gr ... speed of sound velocity and if it matters on accuracy for handguns. I saw a article on match vs regular 9mm and their results showed best accuracy in the (bad) transonic area of under 1180 fps at 25 yards which sort of bucks the posters theory of staying above 1210 fps for better accuracy.

It appears other factors outweigh any speed of sound issues for 115gr. 115gr ... even in the transonic region the air turbulence just does not have enough time to disrupt the bullet much in 25 yards ... Has anyone here found a correlation which says it matters?
Click to expand...
In the Handloading & Reloading subforum of THR, we have discussed, range tested and confirmed/myth busted many notions about transonic affects on pistol bullets.

Yes, there is turbulence effect bullet experiences while transitioning from supersonic to subsonic velocities. But as you posted, there are ammunition/reloading and shooting variables that could overshadow and mask affects of transonic turbulence.

Theoretically, to eliminate transonic turbulence, you want the bullet to remain either supersonic or subsonic to target at 25 yards. But can we really see the difference on target of transonic turbulence practically? Not really at 25 yards if ammunition/reloading variables that produce shot group spread of one to two inches stacked on top of shooting variables of another two inches.

Having shot over 600K reloaded pistol rounds over the decades and untold number of 22LR rounds, I have repeatedly produced 2" to sub 2" groups with 22LR/9mm/40S&W/45ACP some of which experienced transonic turbulence. For average shooter, I think it would be difficult to identify influence of transonic turbulence on 3"-4" groups at 25 yards let alone 2" groups as both supersonic and subsonic ammunition/reloads produce similar large spread compared to transonic ammunition/reloads (And for 22LR, I am talking about pistol groups).

Load development threads for 2"/sub 2" 25 yard groups with 9mm/40S&W/45ACP - https://www.thehighroad.org/index.p...ts-and-discussions.778197/page-6#post-9924922

25 yard groups with GSG 1911 and 36 gr Armscor HP (1247 fps)

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When I started reloading for PCC (Pistol Caliber Carbines), I noticed additional factor that significantly added to group size at further distance of 50 to 100 yards - Bullet drop.

When I did initial load development for carbine loads, many posted that accurate loads in pistols should also be accurate in carbines. Well, that was not really the case as many 124/147 gr subsonic loads experienced so much bullet drop at 100 yards that I saw up to 6" to 10"+ bullet drop and large spread in group size.

So I went back to 50 yard testing with lighter 115 gr bullet to reduce bullet drop and tested lighter 100 gr bullet to reduce bullet drop even further. (Since my PCCs were blowback action, I also had to content with using faster powders and heavier buffer weight to increase dwell time before bolt/buffer moved back from chamber - But this is for different thread discussion)

These are 50 yard 10 shot groups from 17" Just Right carbine that correlate with magazine review of JR carbines producing around 1.5" groups. The muzzle velocities are supersonic (Just under 1500 fps) and stayed supersonic to target with less bullet drop than 115/124 gr bullet loads.

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And Promo load produced this 10 shot group at 100 yards. (Why 10 shot groups? Let's not talk about 5 shot group being a subset of 10 shot group ;))

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In addition to transonic turbulence and bullet drop, I also had concern for rotational stability of pistol bullets which is not that aerodynamic, more like rotating toaster spinning through air but to my surprise, all of my 50-100 yard testing produced nice round holes without elongation or sideways holes so they stayed rotationally stable to target.

Here's one thread on PCC load development by a member who competes in long range/1000 yard matches and we discussed simple reloading variable of neck tension/bullet setback could significantly reduce group size and likely overshadow transonic turbulence - https://www.thehighroad.org/index.php?threads/ruger-pc9-load.859680/

FWIW, here are groups from my initial load development with even lighter 95 gr FMJ (50 yard shooting spot was taken on range day and 45 yard was best I could do) - https://www.thehighroad.org/index.p...endence-from-work.853305/page-4#post-11387109

Impression I got from my carbine load testing is there are other ammunition/shooting variables that will definitely overshadow any effects of transonic turbulence, at least not enough to see on paper. (BTW, PSA has 1:10 barrel twist rate and JR has 1:16 barrel twist rate and has produce greater accuracy - Which is for another thread discussion)

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The thing about that chart is that they are all different loads with different bullets and powders, which in itself can produce different accuracy results because the gun prefers some over others independent of any velocity transition issue.

It might be tricky to test, but one would have to use the same bullet for the test, but at different speeds. Then show that accuracy is affected, or not, at speeds that make the transition verses at speeds that don't. Then it would have to be repeated with different bullets to show the same effect.
 
Agree.
But you can tell that turbulance has to be a small factor less than the others in 5 inch barrels at 25 yards. Basically out of my 4" P99 it tells me I don't have to worry much about velocity being much of a factor and to worry more about load, bullet etc. 1.74" at 25 yards with 115gr in transonic region is good enough for me.
 
Thanks for the nice photos and great information.

With a 17" barrel seems there is much room to tighten those groups up.

I have a PCP pellet gun (Daystate) that can do 1/3" groups at 50 yards with a 16gr pellet. I have a .22s in LR which can come close to it but its very AMMO dependent. Cheap ammo and its 5" groups with good ammo its 1/2".

Yea many things to consider on twist rates. Usually you want the slowest twist that stabilizes the bullet. There are a few decent twist rate calculaters that will let you know if your bullet is stabilized. It could be a red hearing and have nothing to do with the twist rate but the 1/16 is just a better made barrel. 1/10 twist = more friction and heat vs 1/16 I would doubt 1/10 is over spinning it.
 
BigBob1 said:
With a 17" barrel seems there is much room to tighten those groups up.
Click to expand...
Even Atlanta Arm's accurate match ammunition they supply to US AMU match team and other national match teams is only capable of 1.5" groups at 50 yards from test barrel fixture and smallest groups different magazine review of 17" JR Carbine were around 1.2"-1.5" groups so I don't think I could do much better than 1.0" group at 45 yards and 1.5" at 50 yards - https://www.thehighroad.org/index.php?threads/reloading-confusion.873867/#post-11616247

""Elite Ammo - 9mm 115GR FMJ Match AMU - This ammunition is designed for extreme accuracy at 50 yards.

This ammo is used by the Army Marksmanship Unit and the Marine Service Pistol team for service pistol matches.

Accuracy test requirement: 5 ten-shot groups at 50 yards with an average group size not to exceed 1.5 inches."
​
I post the groups I produce as they are shot on target for my load development and powder work up/work down range testing. In fact, for 22LR testing, I captured every 10 shot group pictures with new 10/22 Collector #3 and T/CR-22 out of the box for my ongoing 20+ brand/weight ammunition comparison threads so we can follow accuracy trend as triggers break-in and barrel rifling wears.

Smallest of 10 shot groups averaged larger than 1/2" at 25 yards and 1" at 50 yards - And these are my "real world" 10 shot average results using "real world retail ammunition", not occasional small 5 shot groups produced with match ammunition.

I now use 10 shot groups because 5 shot groups are simply subset of 10 shot groups ... If I stopped at 5 shots, I too can claim 1/2" groups at 50 yards as many of my 10 shot groups started out as 1/2" 5 shot groups ;) and why Atlanta Arms also uses 10 shot groups for their testing (Do a full copy paper shooting with ten 10-shot groups at 50 yards using retail ammunition and I will accept the smallest average 10-shot group size as "real world" accuracy). But in reality, the composite summary of all 10 shot groups is the "true accuracy" with ammunition and shooting variables combined.

10/22 thread (Round count 2960 out of the box) - https://www.thehighroad.org/index.p...lector-3-break-in.859106/page-2#post-11351163

T/CR-22 thread (Round count 600 out of the box) - https://www.thehighroad.org/index.p...mmo-comparison-break-in.864241/#post-11405528
 
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fxvr5 said:
small round counts are subsets of larger round counts, and the implications of drawing a conclusion from small round counts or focusing only on the smallest group
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I agree and why I switched from 5 shot groups to 10 shot groups for my accuracy testing with several repeated range testings for verification.

And in the "Real World" 22LR testing threads where every 10 shot groups were documented and pictured, I saw the accuracy trend swing from "good days to bad days" and after several thousand rounds were shot, could arrive at a better conclusion as to what different ammunition will "average".

One example is Remington Thunderbolt which occasionally produced really tight groups on par with CCI SV but also produced larger sized groups while Aguila LRN/CPRN produced more consistent group sizes over time.

So when conducting load development or ammunition evaluation, drawing conclusion after a range trip based on limited number of 5 shot groups may not properly represent the true accuracy "average" of the ammunition not to mention the factor of shooting variables.

As fxvr5 posted, Ransom Rest anchored to concrete block is really nice to have for accuracy testing but most of us lack such resource and may have to rely on greater sample size instead to identify more accurate ammunition.

fxvr5 said:
And 10 shots is a subset of 11 shots. ;)
Click to expand...
Definitely. And members jmorris and Bart B. both endorsed larger group sample size and to factor everything, including flyers into group size calculation. As jmorris expressed, even 50 shot group is subset of 100 shot group.

As you have posted previously, larger sample size do provide more accurate information and single, even a few 5 shot groups may not be adequate.

fxvr5 said:
A well built 9mm (and 38 Super) 1911 will shoot 10 shots at 1.0" at 50 yards.
Click to expand...
And even smaller than 1.0" at 50 yards with Atlanta Arms 9mm 110 gr JHP.

Pretty consistent ammunition when the same pistol produced 1.5"+ groups with other ammunition.

 
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BigBob1 said:
I saw an old post about speed of sound velocity and if it matters on accuracy for handguns. The thread is closed so can't reply to it.

I think the person assumed since it affect pellet guns that it should affect heavier pistols even at 25 yards. I'm reloading 9mm and at stage 1 (just getting it consistent and not blowing anything up in the process) Now I'm wondering if fps makes much of a difference with 9mm 115gr.

I own Daystate PCPs and know they can be affected if you go too much past 900fps and agree with most of that thread that in theory it should make a difference But I saw a article on match vs regular 9mm and their results showed best accuracy in the (bad) transonic area of under 1180 fps at 25 yards which sort of bucks the posters theory of staying above 1210 fps for better accuracy.

Its putting the 115gr on the edge of too much power (for guns that are not p+) to get them above 1200 fps from a 4" barrel. And subsonic they don't have power.

It appears other factors outweigh any speed of sound issues for 115gr. It could be that the mass of 115gr vs a 16gr pellet is so great that even in the transonic region the air turbulence just does not have enough time to disrupt the bullet much in 25 yards. With a pellet gun and 16g pellet its so light that moving that small mass around by turbulence will have a noticeable effect.

Take a look at this test of match vs non match grade 9mm ammo and see that velocity at 1100-1200 range (which is suppose to be bad for turbulence) had great accuracy and better than some of the faster bullets (1200fps +)

These results are in stark contrast to that posters theory on accuracy and velocity. It might be a factor but it appears that one can load 9mm and not worry about if they are above the speed of sound for best accuracy.

Has anyone here found a correlation which says it matters?

View attachment 938612
Click to expand...

Shoot more, agonize less. Don't overthink it, just go shoot.
 
A word on an article linked to above:

"A common method to test the accuracy of handguns and rifles is to shoot five-shot groups. Sometimes 10-shot groups are used. With rifles, sometimes it’s three-shot groups.

Most gun reviews feature several groups, from three to five for each load tested. Sometimes a single five-shot group is fired for each load, and this seems to be a common method online and in videos. It suggests that a single five-shot group is all that’s needed to know how well a gun likes a particular ammo. It’s not. Even several five-shot groups have limited value."

https://www.ssusa.org/articles/2019/9/25/accuracy-testing-shortcomings-of-the-five-shot-group/

The above is incorrect. The standard method of checking a handgun for accuracy is 5, 5 shot groups at 25 or 50 yards from a bench rest or a ransom rest for any particular load. This has been the method used by the NRA in it's publication, The American Rifleman for decades now, exceptions being made for snubby's. It's also used in Handloader Magazine.

The author of the piece misses that there is a difference between a "common" method and others where a shooter is looking for more precise measurements. There is a difference. For most persons going to a range it makes no difference if we're shooting 5, 10 or 20 round groups and measuring them. If we plan on going to Camp Perry then the difference between a cold gun and a hot gun can come into play and 1/8th of an inch can make a difference between first place and third place.
 
tipoc said:
A word on an article linked to above:

"A common method to test the accuracy of handguns and rifles is to shoot five-shot groups. Sometimes 10-shot groups are used. With rifles, sometimes it’s three-shot groups.

Most gun reviews feature several groups, from three to five for each load tested. Sometimes a single five-shot group is fired for each load, and this seems to be a common method online and in videos. It suggests that a single five-shot group is all that’s needed to know how well a gun likes a particular ammo. It’s not. Even several five-shot groups have limited value."

https://www.ssusa.org/articles/2019/9/25/accuracy-testing-shortcomings-of-the-five-shot-group/

The above is incorrect. The standard method of checking a handgun for accuracy is 5, 5 shot groups at 25 or 50 yards from a bench rest or a ransom rest for any particular load. This has been the method used by the NRA in it's publication, The American Rifleman for decades now, exceptions being made for snubby's. It's also used in Handloader Magazine.

The author of the piece misses that there is a difference between a "common" method and others where a shooter is looking for more precise measurements. There is a difference. For most persons going to a range it makes no difference if we're shooting 5, 10 or 20 round groups and measuring them. If we plan on going to Camp Perry then the difference between a cold gun and a hot gun can come into play and 1/8th of an inch can make a difference between first place and third place.
Click to expand...

I don't see where the author is referring specifically to methods used by the NRA or any specific publication. It seems more general. Look around at other places and you'll find all sorts of round counts etc. used to assess accuracy.
 
fxvr5 said:
I don't see where the author is referring specifically to methods used by the NRA or any specific publication. It seems more general. Look around at other places and you'll find all sorts of round counts etc. used to assess accuracy.
Click to expand...

That's the problem. He does not point out the difference.
 
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