Comparing pistol energy levels to rifle energy levels is not going to help. The old dirdy/thurdy has more energy out to 100 yards than pistols. Game is killed by shot placement. velocity and bullet weight and bullet type/construction are a very close second and should match the game. Look at the defunct .264 Win Mag it had all the velocity any hunter needed, and it gained a reputation for bullets blowing up on impact, because the bullets in the 60' s where for the most part junk.

With todays bullet technology we can use calibers at the lower end of the scale per animal, if we direct are shot VERY CAREFULLY. But why take the risk of wounding game and have it die latter. Use an adequate cartridge and bullet.

This business of useing .22 cal centerfires on deer, or worse yet boar is ludicrous.
Even worse if you watch the outdoor channel you see hunters in Texas promoting this BS about 60 grain bullets @ 3500 fps for deer, and of course it always drops them in their tracks, at least on camera I wonder how many just got " creased" or " nicked" sure there be all right[X(]. The slow death put to game by wounding does not make us hunters look to good, this is bad for us all[:' (]