Just because a certain cartridge will kill an animal doesn't mean that it's the "right" thing to do in using it. I once killed a deer with a 22LR, and yes, it was illegal. An old farmer I knew lived off deer meat, and all he used was a 22. But, a 22LR is a very poor choice as a deer rifle. I am old school, and remember when the 243 was smallest centerfire cartridge you could use for deer hunting here in Kentucky. I think it should still be that way. By the way, I've killed a few deer with the 223, but I still think it's too small.
What cartridge and bullet do you prefer to shoot deer with, and out to what ranges?
