MechAg94: Not so much the weight by itself, but I've handled full-sized M-14s that were better balanced than M-1As, and thus feel lighter than, the Springfields, including the SOCOM rifles.
As for the mud and sand: Take a good military rifle, like an AK-47, and look at the original way its built. Tolerances? Who needs tolerances? The thing can be buried in wet sand at the beach for years, taken out, rinsed off, and a magazine can be shot through it. It won't hold a group as well as an AR rifle, but it will likely work. Take the blueprint for the AK, have an American Craftsman go over it and build one, you'll get the accuracy you want, but you probably won't be able to bury it at the beach and get it to function flawlessly time after time.
The difference is in tolerance. M-14s, Garands, lots of originally military rifles (not counting the M-16, unfortunately) have loose tolerances. Springfield caters to folks who crave a rifle that will outshoot them. They make a great gun, no question. I just would rather have a GI receiver and parts than a precision fit one, at any price, for the combat purposes which that style rifle was designed. In my opinion (yeah, yeah, everyone's got one), if you want accuracy and smoothness, go with a Remington 700 or a Winchester 70, tune it up, spray honey on a target and shoot flies at 200 yards.