Docgkr please correct me if I am wrong, but in reading up on reloading, I believe the problem is with rotational velocity. Basically the bullet can spin fast enough th over stabilize ano/or disintigrate if flight.
There is a 1:8 twist used on mstn's mk12 upper. This is supposed to do great with most available .223 projectiles. Again, don't quote me unless someone more knowledgeable than I speaks up.

