I had probably run close to a thousand rounds through a Garand before I was drafted and went through Basic with the Garand in early 1954. What I remember about the makeup of our Battery at Fort Bliss was that about half the guys--4th Army area, southern US--were "citified"; about half were of country background. Roughly.
I was startled at the general lack of interest in shooting, on the part of many of the city guys. For me, a day at the range was the best part of the deal. But my recollection is that quite a few of us with any background in shooting had no trouble in scoring pretty high, on up into Expert.
Those old Garands weren't bad shooters. Sometimes the marker-guys in the pits wouldn't mark your shot. Lazy goof-offs. So, I'd just hit the 2X4 of the target frame and let them have a few splinters, or just graze the gravel at the top of the berm and "throw rocks". That tended to get them back to work. (Giggle-snort)
My Field First Sgt. had done two tours in Korea. He could make a Garand chatter just real quick, hitting spread-out targets at various distances about as fast as any semi-auto ever could. I've always been pretty darned good at one-shot kills at pretty fair distances, but that guy could ruin a squad of enemy in a heartbeat. He impressed the heck out of me, for sure.
As far as highly skilled shooters, a competition military-rifle match just before WW II had the US team impressed at the speed of the Brits with the SMLE. They'd flip the bolt up with the index finger and slam home with the cock-on-closing. The rates of fire were roughly equal. I think Keith spoke of this in his "Hell, I Was There". I've read of it elsewhere, though.
FWIW, Art