The first thing that you need to do if you are not doing a bolt conversion is have the head space checked accurately. That will tell you if you can safely fire both 7.62 and commercial .308, or neither. I shoot both through rounds through both of my M14's because they are head spaced to do so. One by Fulton and the other, Tim at Warbirds. The only thing you
MUST NOT do with commercial ammo is to shoot light magnum or magnum loads. I shoot standard Remington 150 gr Corlok rounds all day. I also shoot 168 Federal Premium and Black Hills ammo. There is no problem. Go here to learn more about the M14 platform than you thought possible.
http://m14tfl.com/upload/ Hope this helps.
Ken