You'd think that the .243 was some kind of pipsqueak, everyone seems to think it needs premium ammo to bring down a deer?!
I've used the .243 on deer and pronghorns since 1978. Dozens of animals (including two elk) later, I can tell you quite frankly that the .243 does NOT need premium ammunition to be effective on deer-sized game.
Focus on your marksmanship and on finding a recipe your rifle shoots well.