Re: DPMS 308 SASS ??
I have a DPMS Sass upper, it is MOA or better with good ammo. Typical grouping for me is 3/4" 5 shots at 100 and 1 1/2" at 200 using handloads. Velocity is acceptable for an 18" 308, 2500fps is about max with a 175+ weight bullet. It's not "match" barrel though as the consistency and higher velocities I see out of match barrels just aren't there.
Are you buying the whole rifle complete? It's not a bad setup if you are getting a decent price but keep in mind a lot of that extra money is going towards features like the flip-up sighs, PRS stock that some of them came with, etc etc. So if you want those features then great, but if not you should consider buying a stripped lower and then building your own upper instead. That's what I wish I had done.