BCM KD4 upper question

[ggammell]

The .0779 number represents difference in bullet revolution while in the barrel. How many revolutions the bullet makes while in the barrel isn't what we're talking about, and is not what determines stability. Rate of twist is what the barrel twist numbers represent. For a given velocity of a bullet at the muzzle, length of barrel doesn't effect rotational velocity. Hence, rate of twist. I may need to go back to school to do the math on the difference in rotational velocity between bullets at a given velocity exiting 1:7.7 vs 1:8 barrels. However, the difference in twist rate between those same two barrels is 0.3.

Hence why I said “more twist” not “rate of twist”.

[ggammell]

Ok here’s the verdict from Kyle:

It’s a barrel twist that he has selected after trial and error from every barrel twist from 1:6 to 1:8. It is specifically optimized for the BH Mk262 Mod 1 ammo. He says it gives about a half MOA more precision over say a 1:8. It’s important to know that the BH loading is not the same as a standard 77gr SMK load which is why his rifling is so specific.

[ssc]

Thank you for the update.

Cheers, Steve

[Furbyballer]

So a buddy of mine and I each own one of these uppers. I can tell you that compared to different 16in barrel lengths out of similar ARs (16" DD, 16" Criterion, 16" Krieger) the KD4 upper had the fastest velocity numbers with black hills 77 smks and tmks. We ran both uppers through a Buck doyle class and he couldn't believe how fast our 16in guns were performing. As to accuracy, these barrels are sub moa 10 round group guns, which is about the best compliment I can give a 556 gas gun. I own very few 556 barrels that meet that criteria.