Just my opinion, But a 1 MOA gun at a 100 yards is going to have trouble if not impossible to keep 1 moa a 600. I know it can be done, but from my experence you need something close to a .5 MOA gun to hold 1 moa at 600 yrds. It looks like it should on paper, but if the gun is not shooting well or the shooter it or you would be lucky to hold 1.5moa with all the variables.
Maybe I am a piss poor shoot but my .75 MOA PSS 308 has trouble holding 1.15-1.25 moa at 600 due to variables. Will it hold 1 moa some times yes! but on avarage it will not. Shoot with it at that distance and be HONEST WITH YOURSELF!
And who cares if it will hold 1 moa..the first shot is the important one! If I do not hit on the first shot I could care less what the rest do. Any one can walk it on to the target!
Just a quick story--A guy shows up at our little 600 yrd fun shoot with a Christansen Arms 300 WSM
with a Leupold VX7 boon an crocket recticel. He shot 10 shots and could hardly keep them on a 6 X 6 carbord target backer..Thats in feet by the way! Out of Pure luck he hit an X ring (1 MOA target). Before that shot he had not been close..Packed his gun up and said its ready to 600 yrds for my goat hunt in Russia, and walked out! I can not make a story like that up!