Why would you build a 7 twist 223AI to shoot 40's if you've heard of jacket shedding in mid flight?
Varmint bullets have thin jackets and they'll often kaboom in mid flight from centrifugal force out of 7 twist barrels. Sierra even mentions it in their manual. I was skeptical, so I tried it. Nothing but a puff of dust half way to target. 75 to 90 have shot great.
