Yeh, I would just like to re-iterate that they don't mean is will shoot sub one inch groups at 600 yards, MOA at 600 yards would be 6 inches. So they are saying that the gun will shoot better than 6 inch groups at 600 yards. I think a lot of that is going to depend on the load you are using though.

I think the reason they don't just rate it at 100 yards is because you could easily have a gun that will sub MOA at 100 yards but not group very well at 600 yards. Same thing can happen with a rimfire, it will shoot ragged holes at 25 and 50 yards but stretch it out to 100 yards and it might only shoot 3 inch groups with the ammo you are using. I have seen it happen many times.

Muzzle loaders and slug guns are very bad for this. Don't just assume that because you can shoot 1 inch groups at 100 yards that the same gun and load will shoot 2 inch groups at 200 yards. My Remington muzzle loader would shoot honest to God 1 inch groups with 300 grn XTP's at 100 yards. I tried it at 150 and I couldn't hold a 8 inch group with three shots consistently. I had to change bullets and work up a new load to get it accurate enough out to and beyond 150 yards.

Always beware of a sub MOA claim, if they don't specify what distance they could mean sub half inch groups at 50 yards in a shooting tunnel with the barrel and action in a shooting vice.

Paul