Your posts are very articulate. I have not had your problem with my 3 Garands. I've used Lake City and Greek (HXP) ammo and my reloads using that brass plus my supply of WWII era brass. The only problem I've had was with the H&R doubleing. I think that was mostly my fault since I've also had that trouble with some of my single trigger double-barreled shotguns. I fixed the H&R by replacing the trigger.

I wonder if you've thought of swapping some parts with your Springfield to try to see which part is the culprit. Also, I guess I'd try die marking (magic marker,etc.) loaded clips and inserting them in both rifles to see if unusual rub marks appear.