Factory Ammo Chrono Results from Various Barrel Lengths

[Sensei]

All data points are 5-round averages +/- STD fired at 80-85F and 30-35 mmHg BP.

1) Hornady .223 55 grain TAP GMX from 16" Steyr AUG (1:9): 2924 +/- 12 fps.

2) Hornady 5.56 NATO TAP GMX from 16" Steyr AUG (1:9): 3159 +/- 13 fps.

3) Hornady 5.56 NATO TAP GMX from 16" X95 (1:7): 3201 +/- 22 fps.

4) Hornady 5.56 NATO TAP SBR 75 grain from 10.5" LMT MRP (1:7): 2169 +/- 7 fps.

5) Hornady 5.56 NATO TAP T2 from 10.5" LMT MRP (1:7): 2423 +/- 19 fps.

6) Hornady .308 TAP 168 grain AMAX from 20" LWRCI REPR (1:10): 2531 +/- 28 fps.

7) Federal .308 168 grain GMM from 22" GAP HRT (1:11.25): 2669 +/- 21 fps (2693 +/- 7 suppressed with SOCOM-2)

8) Federal 300 WinMag 190 grain SMK from 24" AI AXMC (1:10): 2963 +/- 13 fps.

9) Winchester 5.56 NATO Ranger 64 grain RA556B 16" X95 (1:7): 2915 +/- 10 fps.

10) Winchester 5.56 NATO Ranger 64 grain RA556B 10.5" LMT MRP (1:7): 2506 +/- 8 fps.

11) Winchester 5.56 NATO Ranger 64 grain RA556B 10.5" LMT MRP (1:7) and SF SOCOM Mini2 Suppressor: 2544 +/- 22 fps.

12) Black Hills 5.56 NATO 77 grain SOTM 18" Noveske SPR (1:7): 2772 +/-14 fps.

13) IWI Razor Core 5.56 NATO 77 gain SOTM 18" Noveske SPR (1:7): 2772 +/-13 fps.

14) Barnes VOR-TX .300BLK 110 grain TAC-TX 9" Sig MCX (1:5): 2123 +/- 14 fps.


Note the anemic velocity from the Hornady 75 grain TAP SBR. The .300blk launches 110 grain pills at the same speed despite having a 1.5" shorter barrel. Thus, I've stopped using the TAP SBR and will be sticking with the RA556B for all of my SBR needs since it reportedly expands down to 1600-1700 fps. Also, note that the IWI Razor Core has essentially identical velocity to the much more expensive Black Hills load. My accuracy testing reveals the IWI load to approach the Black Hills load. Bottom line, IWI is some good stuff at a fraction of the price.

[SeriousStudent]

Very interesting. When you were shooting the Hornady TAP SBR and the Ranger RA556B loads out of the 10.5" barrel unsuppressed, did you observe a noticeable difference in muzzle flash? I'm planning on shooting the 5.56 loads out of a suppressed 11.5" AR, but am always aware I might need to take the can off sometime.

Thanks again for the data and analysis.

[Sensei]

There is a small difference in flash, recoil, and gas (when suppressed) between the TAP SBR and RA556B but not enough to justify the 250 fps give away to other 75-77 grain 5.56 loads and 325 fps to the RA556B. To be honest, I can't tell the difference between the TAP SBR and .223 loadings...

[SeriousStudent]

Very cool, thanks again for the information.

[Sensei]

You are welcome. FWIW, I've been very pleased with the RA556B. It's reasonably accurate and feeds in all of my guns EXCEPT my AUG which seems to do fine with 55 grain GMX. At first, I was a little skeptical of the Ranger's ability to feed given its more rounded profile. Plus, I'd heard that bullets having exposed lead tips were prone to suffer reliability issues due to deposits on the feed ramps. However, I've not had this issue with several hundred rounds fired. Another plus is the RA556B is it seems to be one of the few full power, 5.56 loads with an excellent preforming bullet that is also reasonably available from multiple online vendors.

[LOBO]

Thanks for taking the time to put all of this together.

[okie john]

I find that every firearm is a law unto itself, and I'm very hesitant to take any chronograph data as gospel unless it came from the rifle I'm interested in. For instance, I have three 30-06 rifles: a Husqvarna 1640 with a 22" barrel, a Tikka T3x Lite with a 22.7" barrel, and an FN Mauser with a 24" barrel. Federal's cheapest blue-box 180-grain load runs 2,665 fps in the Husqvarna, 2,630 fps in the Tikka, and 2,610 in the FN Mauser, or the reverse of what you'd expect. But these three rifles don't always fall in that order. With 150-grain CMP M-2 ball, the Husky runs 2,786 fps, the Tikka runs 2,721 fps, and the Mauser runs 2,765 fps.

If you don't clock a load in a specific rifle, then you're just guessing at velocity.


Okie John

[Sensei]

I find that every firearm is a law unto itself, and I'm very hesitant to take any chronograph data as gospel unless it came from the rifle I'm interested in. For instance, I have three 30-06 rifles: a Husqvarna 1640 with a 22" barrel, a Tikka T3x Lite with a 22.7" barrel, and an FN Mauser with a 24" barrel. Federal's cheapest blue-box 180-grain load runs 2,665 fps in the Husqvarna, 2,630 fps in the Tikka, and 2,610 in the FN Mauser, or the reverse of what you'd expect. But these three rifles don't always fall in that order. With 150-grain CMP M-2 ball, the Husky runs 2,786 fps, the Tikka runs 2,721 fps, and the Mauser runs 2,765 fps.

If you don't clock a load in a specific rifle, then you're just guessing at velocity.


Okie John

When accounting for the standard deviation in a 5-shot group of factory ammo, there is surprising little difference in velocity between similar length barrels when comparing the same bullet. For example, a sample comparison of means between the 55 grain GMX fired from a 16" barrel X95 and 16" AUG (numbers 2 and 3 above) reveals a p-value of 0.1029. That means there is a 10% chance that the observed difference in mean velocity is due to random chance - not statistically significant when using a conventional scientific threshold of p<0.05.

When talking about practical applications, there is even less diffence in the two means when it comes to terminal performance and external ballistics.

[okie john]

When accounting for the standard deviation in a 5-shot group of factory ammo, there is surprising little difference in velocity between similar length barrels when comparing the same bullet. For example, a sample comparison of means between the 55 grain GMX fired from a 16" barrel X95 and 16" AUG (numbers 2 and 3 above) reveals a p-value of 0.1029. That means there is a 10% chance that the observed difference in mean velocity is due to random chance - not statistically significant when using a conventional scientific threshold of p<0.05.

When talking about practical applications, there is even less diffence in the two means when it comes to terminal performance and external ballistics.

I did not know that. I defer to your experience.


Okie John

[Sensei]

Another data point.

15) Barnes VOR-TX .300BLK 110 grain TAC-TX 5.5” Sig MCX Rattler (1:5): 1827 +/- 21 fps.

Conditions 53F, 100% humidity, 27mm Hg.

Of note, the second round came out at 1792 FPS which was a significant outlier with the other rounds in the string being 1846, 1841, 1834, 1823 (1836 +/- 10 FPS). Bottom line, a 5.5” barrel gives up ~300 FPS to a 9” barrel using the Barnes 110 TAC-TX. Keep in mind, this round expands down to 1400-1500 FPS which means ~175 yards assuming a conservative muzzle velocity of 1800 FPS.

[Sensei]

And another...

17) IWI Razor Core 7.62x51 NATO 175 Grain BTHP SMK OTM fired from 16” 1:10 twist Barrett MRAD:
2398 +/- 36 FPS.

78 degrees, 50% humidity.