Two inch group is not much of a accuracy requirement,On the other hand, long range target shooting equipment will need to have sub MOA accuracy.............
In professional sniper rifle, I guess - one shot - one kill rule applies,
In conclusion, I would say - sub MOA accuracy for longe range target shooting and sniping. Plus MOA accuracy for hunting.
Not sure I agree with most of what you posted. Carlos Hathcock had a Model 70 target rifle that was in fact a 2 MOA rifle. He did quite well.
I really doubt Simo Häyhä's iron sighted Mosin was near that, he did quite will.
Military snipers are taught to aim center mass. The average width shoulder to shoulder of a soldier is 19 inches (hense the measurements chosen for the E Shillotte target 19 X 40).
A 2 MOA right is good on that target to 950 yards. The vital area of, lets say an antelope is about 8 inches. That same 2 MOA is only good for 400 yards.
To refine it further I use to with Alaska Natives to hunt seals in the Bering sea. Normally you only get a head shot on those little buggers bobbing around in the water, that's about 3 inches. The 2 MOA rifle is good for 100 yards. Try to get that close and the suckers dive.
LE Snipers or to be PC Counter snipers are taught head shots, (different ball game then military snipers). The round needs to be kept inside 4 inches to be effective. In theory thats 150 yards, BUT, you probably wont get that, you'll get a partical head behind a hostage, 1-2 inches if you're lucky. That brings you back to 100 yards or under.
I don't put much stock in MOA size, because as I posted several times, you see people posting sub MOA groups with their rifle all the time, but you see very few "Cleaned 1000 yard targets". The X-10 ring on the NRA 1000 yard target is 20 inches or 2 MOA.
So what does this mean?.......................ITS THE SHOOTER NOT THE RIFLE.
And its not only the ability to judge wind and other weather conditions. Best example here is the CMP GSM Vintage Military Matches that are shot at 100 or 200 yards. Wind 'n such is not a big handy cap here.
Just about any diecent surplus military rifle is good for 3.5 MOA, and that's the size of the targets used in the GSM matches, X-10 ring being 3.5 MOA. Again, very few cleaned targets.