The 1 in 12 twist rate is definitely going to appeal to varminters and short range target shooters. The Valkyrie was designed from the start as a fast twist, heavy for caliber cartridge, so the slower twist rates will make it a hard sell. The .220 Swift with the 1 in 9 should work with bullets approaching 80 grains, because of the high velocity it offers. I Think the best bet is 12 twist .223 specifically for varmint bullets 60 grains or less, then either the .22-250/also AI version on the 10 twist for bullets up to 69 grains. The short 21 inch barrels are going to rob velocity from all the cartridges, but less so in .223.