prototoolman.... perhaps you will post photos of your SP-101 with a .357 Maximum shotshell. Reckon that would raise havoc with a rat running across your bookshelf. I'm for anything that kills rats, anything except poison. I can't abide the idea of poisoning a rat, followed by an ermine (weasel) or other fellow predator dining on the rat. Most poisons are a gift that keeps on giving. Mink, ermine, martens, and fisher cats, etc.----along with proper rat murdering dogs----inflict a special enmity on rats, an enmity I respect. I've used enough poison on termites to last a lifetime, and if I never touch the stuff again that will be soon enough.
Back to your pistol. Handled, years ago, a Colt Model 1917 .45 ACP, with bored through chambers, all six, to accept with half-moon clips .30-06 brass cut off just shy of the cylinder face and loaded with bird shot. The bore had been reamed clean of rifling. I was young at the time and unaware that a pistol without rifling is a no-no. Hell, the conversion may have been done in the wake of World War I, but when I saw it it was a no-no.
Your revolver sounds legit, so the question arises, how does that long shot column pattern at 12 feet?
David Bradshaw