Hello, My name is Logan and I am considering using a Stillers predator extreme or tac 338 action for a custom rifle in 338 lapua or 338 allen xpress and had a couple of questions. Will either of these actions accept a barrel with a shank diameter of 1.225"? Will this size barrel leave enough of a shoulder to properly clamp the recoil lug in place? Can either of these actions be had as a singleshot? Lastly do rem 700 picatinny bases fit these action. Thank you for your time.