I like the saying that we seem to always worry about the wrong things. In everything. That sure applies when choosing a caliber.
Millions of printed gun magazines have been sold with cover lines screaming "9mm VERSUS 45ACP!" and such. It's fun to talk about, but the bottom line is that it just doesn't matter -- within wide guidelines, of course.
Not for self defense. There's no statistical difference in stopping ability between the 9mm, the .38 Special, the .40 S&W, or the .45ACP. Even the .380 is pretty much in there with those stalwarts. On average, it seems to take about 2.5 hits from a handgun to stop an attacker. With a rifle or shotgun, it's about 1.5 hits.
For hunting, it's the same. For deer, I'd start with the .243 and end up with the .338 Magnum. I've killed whitetail with both. Anything between them is fine as long as you shoot it well. And there it is.
Stop stressing about caliber and "worry" about the important stuff. Like practicing all the time. All. The. Time. Dry firing your handguns and rifles (yes, for hunting). Draw and click. Reloading drills. Malfunction drills. Taking your hunting rifle off the sling on your shoulder and getting the crosshairs on target, then pressing the trigger without disturbing your aim. Do THAT 1,000 times and the cartridge won't matter because the bullet will go in the right place.
Recoil is a much bigger factor than many people realize. Many hunters use cartridges with too much recoil, and they can't shoot them well. Want to be a better game shot? Go with a less powerful round. The 6.5 Creedmoor will do it all if you use the right bullets. Ditto .257 Roberts, 6.5x55, .260, 7mm anything, 30-caliber whatever.
Shoot. Shoot. Shoot. Shoot. Shoot. Centerfire. Rimfire. Air guns. Airsoft. Dry fire. I've read that it takes 10,000 repetitions to achieve excellence. Do it 50 times a day (dry fire or air guns makes that easy), and you are at "excellent" in only 200 days! ~ Tom
Author, outdoorsman, gun rights activist, and firearms enthusiast for more than five decades, Tom Gresham hosts Tom Gresham's Gun Talk, the first nationally-syndicated radio show about guns and the shooting sports, and is also the producer and co-host of the Guns & Gear, GunVenture and First Person Defender television series.