There areshot shells made for a variety of handguns- I have .45s and .38 Specials at the moment- as well as .22 LR and .22Mag.
It will NOT hurt your barrel. If you shot a LOT, you would need to scrub barrel (many have shot in a plastic capsule- you will scrub plastic out of barrel)
Due to the spin imparted by the rifling (as that fellow just said up there ^^) the shot column is thrown open, and at any great range, looks like a doughnut. IMHO, effective range for .22LR is about 10 ft, 22 Mag 15 feet, other handguns, about 20 ft.
While most shot loads will not cycle a semi, there WAS a 45 ACP shot load made for the Thompson SMG that fired full auto. Was a "riot control load". Still recall the ad copy from Auto Ordnance- "Calm a raging mob with the gentle patter of bird-shot". Yeah- fired full auto. OWTCH!!!