Because both my dad, brother, and I are going deer hunting this shotgun season, we are having a shotgun shortage around here. Not wanting to go out and buy another one, we were thinking of one of us using our 20 gauge. But here's the deal. It is a single-shot, smoothbore, full choke, bead sight bird gun. Would it be wrong for us to fire rifled slugs through this gun? We are planning to use it in a blind for making shots under 30 yards or so. Please tell me if this is a wacky idea.

Why wacky????

When i was younger, that was the "only" option, and everyone did it, and we killed a lot of deer that exact way!!!

Use plain lead slugs, and try a few brands to see what one shoots best..

Drilling Man

Ok, maybe we aren't as crazy as I thought.

Yesterday we fired several lead slugs out of the bird gun with surprising accuracy. Using only the bead on the end of the barrel, my brother hit a two-inch circle on a target 40 yards away. Any uncomfortablness I had about hunting deer with this gun has since vanished.

As you appear to have discovered, there's nothing wrong with using slugs in a 20-ga. As long as you use the Foster or Brenneke type slugs, they will pass through a full choke with no problem. IMO, the Brenneke slugs kill a lot better than the Foster type, so use them if they'll shoot accurately in your gun.