Im buying my lapua next week. But I heard about the allen magnum shooting a 300 gr @3500 fps. And was wondering after I buy my savage 338 if I find myself wanting more will the 338am fit in this gun and the ai magazine? I read you can modify the mag to fit the longer lapua shells. Just wondering I couldn't find the rim diameter or coal by google. But I seen pictures compared to other calibers. Its a monster to say the least.