Fred Routledge developed a back bored .22 smooth bore, with the last 12"-17" of the barrel around 3/8" bore, to give the shot charge sort of a "jug choke" effect. The Mo-Skeet-0 was a mini skeet set up for .22 shot rounds.
Not many Routledge bores were made. I've been looking for one, so far, no luck. There were a few Rem 141 pumps so equipped. They had a small bead, no rifle sight.
I've been contemplating shooting boring (carpenter) bees at my house with an 8 3/8" K-22 and shot ctgs. I've been knocking them down with a swatter I made, but shooting them will be more fun.
DF
