converting snider smoothbore to what caliber?

[justashooter]

so what caliber can we convert a snider smooth bore to with a barrel insert? the bore is about .590 and i have a lathe so sweating a liner in from the muzzle would be no big deal. and extending the extractor wouldn't be hard.

what caliber? something around 1.75" length...less than 1000 foot pounds of energy...44 special maybe....a stub job sweat in with a different stock styling entirely and maybe a different lock-works? i have some 30-30 and 38-55 and 357 mag barrels handy, and a 444 marlin barrel...

what thread pitch adn diameter and right hand or left hand threads on this thing?

a sweat in large bore rifled barrel to make the howdah pistol legal? the antique action is a non-gun, legally, as an antique...a 50 caliber muzzle-loader barrel chambered to 50-45?

[Texas by God]

It would probably make a fine trapdoor level 45-70. Any cartridge with less pressure than .577 Snider can be made to work.

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[Ballistics in Scotland]

Well leaving aside the possibility of making it into a pistol (and I don't think any kind of howdah pistol but a double made it into a howdah in the great age of howdahs), I would much prefer to use a cartridge contemporary with, and suitable for, the Snider action. The original howdah pistols were frequently in a much shortened version of the Boxer .577 cartridge, as also used in the monstrous Webley .577 revolvers.

All of the cartridges you named are frequently loaded to pressures too great for the Snider, and firing-pin diameter and fit would probably be an issue too, and you never know what some member of the intellectual classes yet unborn might do with the gun. The .50-70 US government would be more likely to instil a measure of caution, and even a custom loader of ammunition is likely to assume the customer has a trapdoor.

My own choice would be a shortened .450 Express, the straight-cased version, which was usually 3¼in. in case length, but was made down to 2½in. and possibly shorter. I would also keep it as a rifle, for Mr. Snider surely wanted it that way. I also suspect that the pistol idea and other changes would be piling up a stack of "debatables" if it is necessary for you to own an antique by US legal standards, and that sort of thing can be a lot of time, trouble and worry even if you win in the end.

You can get a wide range of bore liners from www.trackofthewolf.com or from TJ's, who make them for Track. Most of the relevant ones are 5/8in. outer diameter. You could ream .590in. to the necessary .625in. with a hand reamer extended by a hole drilled in the butt with a carbide drill, and a steel rod soldered in. That end is often softer than the tip. Alternatives would be to adapt a rotabroach cutter or turn down the liner. But you would have to add some sort of larger diameter sleeve or extension for the chamber. Current practice is more often to fit the liner with one of the bearing-fitting versions of Loctite rather than solder.