The story is set in the United States/Canada, early 1990s. The character with the shotgun is a 13-year-old boy. From what I've read so far, I've determined that someone his age would probably best handle a 20-gauge shotgun. It'll be a pump-action (the break-action seems too clumsy for this situation and a self-loading would be way too expensive for this character), with a sawed-off barrel so it'll be short, probably about 14 inches.
He's going to need to fire three shots in fairly rapid succession. The first one will be a distance shot of at least 20 feet. The next two are going to be very close range: the second at about two feet, the third almost point-blank. On the third shot, he's going to have to fire UP at his attacker while lying on his back. The target is something about as big as a grizzly bear, that walks on two legs but is much faster than a bear. The kid knows how to handle himself around guns, he's not a novice.
1) What's the maximum range of a shotgun while maintaining effectiveness? I've read that, unlike rifles, shotguns are not really good for distance shooting. For that first shot, can the target be MORE than 20 feet away, or is that already too far? (I DON'T want to kill or knock down the target on the first shot.)
2) Since shot spreads out once fired, is it even possible for the kid to fire at almost point-blank range without injuring himself? Is it possible for him to do so while on his back, firing at something above him? Is there any "blowback" of shot? Would it leave any visible marks/powder burns on his hands or face?
3) What happens to the spent shell when you pump the forearm? Could this be a possible source of injury to someone in such an unusual shooting position?
4) What sort of wound does a 20-gauge shotgun produce at a distance? At two feet? Point blank?
5) Does shortening the barrel change the gun's range or power?
And finally a generic question:
6) The pump-action shotguns I've looked at all seem to be single-barreled. Are double-barreled shotguns all break-action?
Thanks for your help!