RE: 22 mag deer
I think you need to question you instructor in what he said.in most states it is illegal to shoot deer with the 22 mag.i that is a rim fire shell.f he is promoting this you would need to call the DNR or wildlife dept. in your state and have a talk with them.
as gorse said,it depends on the shot and who is shooting.you can take a bull (cow) with a 22 short;thats what they used in slaughter houses for years to kill cows and hogs.that is not what hunters use.
he may have ment 22 cal. not nessery 22mag. there is a big difference. there are 222,223,243 and so on in the 22 cal rifles.
I am not a hunter ; I am a whitetail population reduction specialest
remember keep your back to the sun, your knife sharp, and your powder dry.