I'm using Sierra 63 grain softpoints in my 1:12" twist CZ 527 .223 Rem. Sierra manual says that this bullet "may" work in 1:12.....seems to work well for my rifle, as I've been getting MOA or better at 100 yards (for the most part) from a nice shooting rest. Doesn't change much w/ the 50-55 grainers, either.