As a lot of those have said an '06 is plenty of rifle. I killed my first elk with a .243. I have a stash of fine rifles in my safe but tend to go with old reliable. Winchester true Pre 64 30.06. I've killed about all a guy can kill with that thing. Also as stated, practice. Try a lot of different positions. Most anyone can sit at a bench or lay down and poke nice groups. I tend to practice kneeling, with sticks, lying on my side, standing, with a tree as a rest, and shooting up hill and down hill at extreme angles.

Good luck and most of all enjoy it.