What is the proper way to shoot a semi-auto 308? From what I understand, The bipod should be slightly loaded and the grip pulled firmly back to shoulder. Is this correct?
On a light recoiling heavy rifle (11 lb. AR 15) is the above true as well?
There are different .308 semi-auto platforms. Most as you noted are AR10s. They are definitely more difficult to shoot, especially if you are inconsistent on follow through, than a bolt gun. However, I have a FN SCAR 20 in .308, and it is literally the easiest gun in any caliber to shoot accurately I have ever experienced, bolt or gas.
I don't know if it is the interface between machine and human, recoil pattern, or what, but it literally took 2 shots to sight it in at 100, and it is dead on for me. Granted, it is a $4500 platform with flawless rifling that has a cold hammer forged barrel and a Geissele trigger, but still. My SCAR 17 with a 1-8 and a Geissele is very easy to shoot accurately as well.
My AR10 is an Aero Upper and Lower, PRS Magpul stock, Vortex Razor HD 4.5-27, with a Geissele SSA-E, Faxon Match Series Heavy Fluted with 5R rifling, and MI FF rail. I am still getting used to it. My advice is keep at it, see what works, keep notes on your phone, and have fun.