A while back I started a thread in the pistol shotshells section where I examined the performance of a large prototype 3D printed shotshell in 357 magnum, and while it certainly worked as intended (a full 1/2 oz, no problem), the dreaded rifling donut was still present. I expressed frustration with this, and said that I wished I could find a neglected barrel to bore the rifling out of. Several folks very rightly pointed out that our idiotic laws would render a single-shot small-caliber low-power short-range gun like this illegal, and I more or less dropped the idea when I realized how expensive it would be to get a minimum-length 38 cal smoothbore custom barrel.
Then one of the posters put up a link to this:
https://www.davide-pedersoli.com/en/...version-pistol
As a side note, why don't more modern pistols look this good? Seriously: Ruger, S&W, somebody... get on that.
Anyway, that got me thinking about an old 45cal Kentucky long rifle my wife's grandpa had given me years ago. It looked nice on the outside once I cleaned it up, but the bore was so pitted that you couldn't hit the ocean with it if you fired it over the waves from the end of a dock. It had just cleaned the bore as well as I could and protected it from rust and there it sat for years, unfired and useless. So... I... got out the hacksaw. And a drill. And many other tools and lubes and various doodads. The goal? A 50 caliber smoothbore something that could shoot donut-free custom shot loads without causing problems with the ATF or my checking account.
In retrospect, I should have bought a long 1/2" drill bit which would have allowed me to drill the rifling out of a longer barrel, but I didn't do that. So, I eyeballed the length of the barrel, the length of the 1/2" bit I had, and cut the thing off. You can imagine how much barrel I removed, those Kentucky long rifles are well named! And then I started cutting and sanding on the stock... and things kind of get fuzzy after that until I found myself epoxy bedding the barrel.
So... this is what I ended up with:
Doesn't hold a candle to the Harper's Ferry conversion linked above, but it does make useful something which was otherwise going to rot in the corner until I threw it away. Or, that's the hope, anyway.
Which is a very long way of starting to ask the question: If this were yours, how would you build a shot load for it? I have about 5000 steel BBs which I'm planning to use (since I don't own a BB gun... don't ask me where they came from) as shot, so I'm not super concerned about the shot being misshapen by acceleration. I have been hunting around and it looks like most normal BP shotgun loads involve an overpowder card, some kind of big fat lubed chunk of felt or something, and an overshot card.
I have a package of these coming:
https://www.midwayusa.com/product/1010391437?pid=814623
Could I just, say, use two as overpowder, slather some bore butter on a third, add a volume of shot equal to the charge, and then a single overshot card?
The other more important question is, what would you estimate is a safe charge for this? It started out 45 cal and is now 50cal smoothbore, but I'm pretty confident that the back area of the barrel wasn't touched by the bit. so it's still more or less factory. The gun tolerated 100gr loads when unaltered but that seems quite a lot for a pistol regardless of condition. I'm confident that pressure in a shot load won't be as high as a tightly-patched ball, but I'm also a BP novice so... well, you know what they say about assumptions.