10.5 vs 14.7 vs 18 Velocity/Powder/Bullet

[Krazykarl]

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

Any speculation on how you were able to get such high velocities out of a 12.5" barrel?

[joeg26er]

The triarc track 2.0 barrel uses single edge polygonal rifling
Now I’m curious what velocity the Triarc 14.5 gets but I’m going to be pretty satisfied with this barrel as it’s light and handy without much velocity penalty