My 6 ARC is my Dedicated coyote rifle and I love it!The 6PPC shoulder is moved forward for a little more volume and a slightly shorter neck. I have full length resized the 6ARC to 6PPC to prove the point. But I have not needed to make rounds that way. Biggest difference in MHO is that the 6ARC specs a twist of 7.5 for those long 100+ grain bullets they are loading commercially. I am not likely to re-barrel my 6PPC, but the 6 ARC does fill an interesting niche. It was designed to extend the effective range of the AR15 in combat with out any dimensional revisions to the platform. Swap some components and you are good to go. I plan to build an 6ARC upper for myself one of these days.