Thought I'd write an update on this thread... since I posted the OP back in '12, I've had occasion to blast a couple of rattlesnakes with the #12 shells, and they kill 'em just fine at a safe distance of 3-4 yards. I also cleaned up a mess of grackles at my buddy's ranch with #8 shotshells as they roosted in the pecan trees. There were more grackles than I had shells, sadly, but I made some more and made couple more trips out there and thereafter the damage to his garden was considerably less.
I don't have enough 44 Magnum shells on hand, though, and since I'll be carrying a S&W Model 69 soon, I am preparing to reload some for that caliber. As it happens, bcolorado recently scored some 445 Mag cases and is willing to share. I'll be loading up some 44 Mag shotshells in these when they arrive, and will post pics again.
Lots of interesting feedback from 24HCF members on this thread on the various ways they've solved their revolver shotshell needs. There's always more'n one way to skin a cat!
