What size reamer would I need to remake a 12 gauge shotgun adapter for 357 maximum?

[huntersdog]

What diameter reamer would I need to ream out a 38 special 12ga shotgun adapter to a 357 maximum cartridge?

Thanks

[Harter66]

You need the leade an throat too . I would suggest a chamber reamer for a 350 Legend or 357 max . If you have a throat reamer then check the cartridge drawing for 38/357& max , .380 as I recall but I've been mistaken before , you'll want about .001-2 over that finished . In a perfect world you'd go groove dia +.001 , plus nominal case thickness x 2 , plus .0015 for bullet release .

[huntersdog]

You need the leade an throat too . I would suggest a chamber reamer for a 350 Legend or 357 max . If you have a throat reamer then check the cartridge drawing for 38/357& max , .380 as I recall but I've been mistaken before , you'll want about .001-2 over that finished . In a perfect world you'd go groove dia +.001 , plus nominal case thickness x 2 , plus .0015 for bullet release . I didn't know if something like that was feasible to do fairly cheap or would it get expensive buying a 357 maximum reamer. I just might just keep it as a 38 shoot it that way.

Thank you very much for your help.

[Harter66]

There are several places that rent reamers . It's like $20 for 7days from tracking receipt to return post mark with a deposit of replacement or close less the rental cost .

Those vendors sometimes offer the 2x sharpened reamers for sale at reduced prices .

Throw up a WTB/WTT/WTR (buy,trade,rent) ad for a Max reamer . There used to be several guys that had them here .

[uscra112]

Careful about renting (or buying)! .357 Max reamers are not all alike. The cartridge was originally for revolvers, so the SAAMI reamer has an undersize pilot and no throat at all. Not good for a rifle barrel. Dave Manson modified one for me to create a proper throat, and sent me a .350 pilot when I set about lengthening a .357 Magnum to .357 Max. Something I wish I hadn't done, as Gen I Contenders can't handle full Max loads. Should have just lengthened the throat so I could seat heavy bullets farther out.

[GhostHawk]

Better off buying a new chamber adapter in .357mag IMO. If needed you could sell the old .38 to recoup part of the cost.

You don't know if that .38 adapter is designed for .357 mag pressures. It might not be.

If it was me I'd go long, 16-18 inches.

[Prairie Cowboy]

With a .357 Maximum cartridge chamber pressure of 40,000 PSI, would this project be wise?

Most shotguns are not built to take these pressures, which is why those who manufacture shotgun adapters are careful to cherry pick the pistol cartridges that they offer, to make sure that they are the ones with the low chamber pressures.

[uscra112]

As long as the hoop strength of the insert is sufficient, it's not the absoute pressure that matters, but rather the bolt thrust. Pressure x area. The .357 is a LOT smaller than a 12 gage. The arithmetic is left as an exercise for the student.

The size of the firing pin in shotguns is another matter.

[charlie b]

How long is that adaptor? If as short as I think then you won't gain anything by going to the Max.