"Stopping power" is a useless concept in firearms.
The only reliable way to stop a machine is:
Hydraulic failure
Structural failure
Electrical failure
The only instantaneous stop, energy-wise, would also cause a flattening of the user, unless you're using a crew-served weapon bolted down. Hand-held firearms have killing power caused by making holes in tissue. Any big game hunter can tell you the power to kill frequently has little relation to the power to STOP quickly. Even a good hit on a 130-lb deer should be followed by at least a half-hour wait, to give them time to bleed out. God help you, if you faced a determined attacker wielding a dangerous weapon. Remember that deer are usually taken by longarms, too, which dwarf typical defensive handgun cartridges in power.
it doesn't matter how large or small your projectile is, the only guaranteed stop is when too much fluid is gone to move, too many/important pieces are gone to move, or no commands to move can be transmitted.<-------------------- (this is a period)
As far as the damage a .22 Magnum causes, from a rifle, especially at short range, a pretty good bit. That damage inflicted reduces as your barrel length decreases.
john