10.5 vs 14.7 vs 18 Velocity/Powder/Bullet

[TomPenguin5145]

So I got curious as to the velocity I was getting from a 10.5 vs my other rifles. I took some rounds I had around and came up with the following. All barrels are 5.56 chambers with 1/7 twist.

Hornady Frontier 5.56 68 BTHP
10.5 - 2495
14.7 - 2713
18 - 2903

Federal Am Eagle .223 55 FMJ
10.5 - 2625
14.7 - 2863

Hornady 68 BTHP 23.0 H322
10.5 - 2390
14.7 - 2625
18 - 2811

Hornady 68 BTHP 23.3 H322
10.5 - 2435
14.7 - 2665

Hornady 68 BTHP 25.1 Varget
10.5 - 2407
14.7 - 2634

Hornady 62 FMJ 24.3 H335
10.5 - 2500
14.7 - 2728
18 - 2808

Hornady 62 FMJ 23.5 H322
10.5 - 2432
14.7 - 2679
18 - 2792

Hornady 62 FMJ 25.5 Varget
10.5 - 2478
14.7 - 2742

[Krazykarl]

200 to almost 300 fps decease across the board for the 10.5. That short barrel sure looks fun to carry. But be careful what you choose for ammunition as terminal ballistics become hampered. What was your perceived difference in report?

[TomPenguin5145]

The 14.7 had a BCM GunFighter Comp on end end and that made it sound louder then the A2 on the 10.5.

[AndyLate]

I am somewhat suprised at how small a difference there is between the 14.5 and 18" barrels.

I have a BCM Mod 0 comp on one of my 16" guns and it will pound my sinuses if I get in the wrong spot coaching another shooter.

Andy

[joeg26er]

Hi - what are the barrel specs? Twist rates, gas length, make/models?
How many rounds did you shoot to get the average?

[TomPenguin5145]

3 rounds of each load for each rifle.

[markm]

The 14.7 had a BCM GunFighter Comp on end end and that made it sound louder then the A2 on the 10.5.

My son was shooting my 14.5 Sunday, and it's barky. There's no concussion to it, but it barks.

[TomPenguin5145]

It was quieter then the 7.5" AR-15 that a guy was using at a low-light carbine class this weekend. :-)

[markm]

It was quieter then the 7.5" AR-15 that a guy was using at a low-light carbine class this weekend. :-)

There's always "that guy" in every class. Did he have an ACOG and Bi pod too?

[joeg26er]

I tried velocity tests on a mid length TRIARC 12.5" AR-15 TRACK Barrel 2.0 with NP3 Barrel extension Chambered in 5.56mm
Slr7 adjustable gas block
Brownells lw nitride bcg
Wolf gold 55gr From 2820-2850
Sellier n Bellot 55gr light green box. 2980 to 2890
IMI 55gr 2823-2750
Tula steel case 55gr. 2780-2816
In comparison on the same chronograph
An hk 33 with 16” barrel ran about 50fps faster
Maximum velocity was 3,000 with the green box S&B 55gr