I have an original one and with standard 1957 Lake City M2, I get about 1.25 MOA.
I think that is pretty consistent for standard M2. Handloads or match ammo can usually get you sub MOA if you do your part.
They can usually shoot. But nothing was really done to them from Remington.
The Marines did have a few and mentioned that if they fitted the stock better by removing wood and free floating the barrel, like they did on the Unertl rifles, and if they tuned the trigger, they performed pretty well.
The main problem of the A4 is the scope. Everyone hated the scope. The field reports detail the scope was horrible, and many complained about the lack of back up iron sights and the ability to quickly remove the scope if it was damage or fogged up. This included the Army reports from Europe.
But the A4 was never meant to be a long term sniper rifle. It was a placeholder as they developed a M1 Sniper rifle.
Honestly after the M1C was fielded in 1945, the documents at the archives basically show the A4's being rebuilt and put into war storage. After 1945 the A4 was basically done other than very sporadic useage.