I like to stay on the safe side with NATO ammo. Nothing wrong with a 1:9 twist, but I stick to my LMT w/ 1:7 twist for NATO rounds or the heavier 77 grain goodies. I've oy shot about 20 rounds of the MK262 stuff (I believe that's the nomenclature). Buddy hooked me up after he went to the All Army rifle shoot @ FT.Benning. With the 55 grain stuff, I never really noticed a difference in groups between my S&W or my LMT.