My aunt used a .243 till she was in her 80's and could no longer climb into her tree stand. The only deer she didn't put down and eat were deer she missed which fortunately wasn't very often. If a little 4'11" gray haired Polish lady can take a deer with a .243 there is no reason why you can't do the same. You are obviously a better than average marksman and know where to shoot your prey just based on your past performance with handguns. Enjoy your hunt and don't listen to the drug store cowboys.
Good intentions will always be pleaded for any assumption of power. The Constitution was made to guard the people against the dangers of good intentions. There are men in all ages who mean to govern will, but they mean to govern. They promise to be good masters, but they mean to be masters.