I had one. I annealed 303 brass and then fire formed it to 410 size. It worked.
I fired a case loaded with a 30 cal leab bullet. This blew out the case mouth. Then I annealed the case and re-loaded with a 44 cal pistol bullet. After that fired, the case was a straight wall brass 410 case.
I blow out .303 brass to make .410 shells just because commercial .410, at $0.75-$1.00/shot is a wee bit pricey to pick off the close in gophers when I'm toodling around in the quad patching fences. I'll take a scoped .22 with me, to reach out to 75 yards or so, but when they're under 10 yards, it's a lot easier to pop them with a .410.
Anyway, I blow out the cases in one shot. Anneal the case, clean, prime, load half the powder from a 12 gauge target shell, wad with a small chunk torn off a cotton ball, fill the rest of the case with corncob tumbler media, seal with another torn off chunk from a cotton ball and a drop of Elmer's white glue.
After that, you can load them as you would any other .410 shell. The case capacity allows for 1/2oz of #7 or #8 shot. Buying powder/shot/primers in bulk, I'm at about 12 cents a shot now for .410 - which is comparable to .22lr nowadays.
Did a couple videos on the process and a write up in the Hunting and Sporting shotguns section, but was roundly ignored by the Fudds there.
Thanks for the replies guys... Sounds like more of a novelty gun from a practical POV, but, fun to play with. What's a fair price for a full-stock? What do you search the EE with... "Ishapore"?
I've seen them at gun shows for $500-$600. Generally speaking, the same few guys bring the same few Ishy .410s to the same gun shows, year in and year out, put them on the table for that price, then pack them up at the end of the show to bring them back for next time.
Soo... you should pay a fair bit less than that.
As for novelty? I dunno. I use a .410 for varminting and small game, just keep the shots within 15 yards and .410 is an effective shell.