Practice, practice, practice......and then practice some more! I shoot my thompson .30-06 religiously and so does my wife. I use either Hornady Custom 150gr soft points or the same grain in hand loads. I nor my wife to date have never had one move more than 20 yds from where it was shot. The key is to get those groups consistently tight toughing if possible at your max range. Aim for the pocket in the arm pit that is, where I have tought my wife to shoot upon gutting you should see a pile of mush where the heart once was. Knock on wood it has been flawless. Also if a deer is in close sometimes the bullet may not have time to perform to its full potential on a very high velocity round.