Old blackpowder SXS with chamber inserts?

simko

simko

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Hey everyone, i see there are a lot of different inserts that some people put in their 12ga shotguns, some adapt different calibers and allow the shooting of pistol and other rifle calibers through a shotgun.

I have seen one site advertising 10" long adapters that are rifled, chambered in calibers such as 45-70 45long colt, 444 marlin 375winchester etc. I was wondering if my old Neumann Bros blackpoweder shotgun would be able to handle these calibers if an insert was added. I personally think this would make for a neat double rifle.
Do i need to reply on the Neumann shotgunstrength? or does the insert managhe the pressure produced by the ammunition

thanks, here is a link about my shotgun
http://www.canadiangunnutz.com/forum/showthread.php?t=325038
 
The rationale that I have used in deciding on whether an action was strong enough for a given caliber was to multiply the chamber pressure by the square of the base diameter of the shell the gun was originally chambered for. Compare that with the same numbers for the intended shell. As an example; off the top of my head, the base of a 12 g shell is about .8" and if you Neumann gun was made in the late 1800s the operating pressures would have been no more than about 6000 psi. That would give a number of 3840. A 45-70 has a base diameter of .502 (call it .5) and if you loaded it to 25000 psi the number is 6250 so part of the answer is that you would be putting about 50% more thrust on the action than it was originally built for.

Obviously you can juggle numbers; by the early 1900s and smokeless powders, pressures had risen to (arguably) 10 or 11000 psi and the gun would probably have been shot with them. Now we are talking 7040 on the Neumann frame or roughly the same thrust as the 25000 psi 45-70.

Also obvious is that you need to check your pressures in loading manuals and not simply load to the hottest load shown but at least it does give you a basis to work on rather than simply saying it is a weak action or a strong action.

As a double rifle you will probably experience a lot of frustration trying to regulate the two liners although you may also get lucky and just have to rotate each liner until you find a pair of positions where they shoot somewhat together.

cheers mooncoon
 
There are a number of ways of doing it but basically fit a filler to the cartridge side of the firing pin hole with a new opening of around .075" and of course make a new firing pin to match. Old firing pins run around .10 to .12" and with higher pressures the primer can flow around the pin and rupture.

The bushings can be threaded into the breach face, soldered or dovetailed depending on personal preferences and how much metal you have to work with. The bushings tend to be fairly thin front to back; maybe .1" thick and are supported by the body of the receiver.

cheers mooncoon
 
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