All of the USGI M14's I've owned, competed with, and accurized had sloppy gas cylinder assemblies. THAT is normal. What did you expect from a battle rifle?
The Norc M14's are all great by USGI standards of sloppy gas cylinders.
Shimming and a few taps with a ball peen hammer on your splines (3 of them) will solve this problem. You are just dimpling the splines, that's all. Have a look at my M14 Clinic CD set (2004 Abbotsford Clinic) and I carry out this mod, I believe.
Cheers,
Barney