most all .50s are capable of 'good' accuracy at 1000yds... really just depends on how much the shooter is willing to put into practicing.
More weight, better scopes, better triggers, better ammo matched to the gun and lots of trigger time learning to read the wind/mirage all contribute to ultimate accuracy at long range.
After much practice with my Serbu, I can usually shoot under 1moa at 1-400yds easily, but only 1.5moa groups at 1000yds with AMAX ammo. I recently got the trigger upgraded to break at 2lbs rather the 4lbs it originally was. Hopefully, that'll help me get my group avg. down below 1moa. If not, then I'll have to concede that the Serbu and me aren't going to be any 'better' at 1000. :) (26lb BFG50 29"bbl, NXS 5.5-22) I'll be trying some new Lehigh hybrid match solids too along with my AMAX loads.
Even the best gun won't do well in competition if the person behind the trigger doesn't do their part well either... :)