I have No 4 two groove that's been sporterized , barrel shortened so no reversal , that I tried some 308 cal 180 gr Nosler Partitions in . I was inspired by an article by John Barnsness in Handloader or Rifle some time back . After changing out the size die expander button to 30 cal I loaded about 20 rounds up . To be honest , I was pleasantly surprised at how well they shot . The rifle is an honest 1.5 to 2 moa shooter with standard 303 bullets , it shot about the same with the 308 diameter bullets . In the article Barnsness stated that the two groove stabilized the under sized bullets better than the 5 groove . Apparently , in his opinion , the larger land area of the rifling combined with the rear section of the partition obturating compensated for the 3 thou difference . I've yet to try them in anything but a two groove to fully test out the theory , but they worked well in my two groove . I'll be trying them out on Moose this fall , we'll see how they work in the field .