IAM building a smoothbore 3/4 schedual 40 stainless barrel and am putting a hooked breech plug into the the barrel,filling in the void with a bushing to take up the play that was tig-welded around the hooked breech threads.Now i was thinking to create a tighter fill in ..Would silver solder....not plumbers solder be strong enough?
I know it's not part of the question but, in my opinion, if you plan on shooting your gun, you chose the wrong material for the barrel.
A 3/4" schedule 40 stainless steel pipe has a burst pressure of 8610 psi and a working pressure of 1080 psi. Both of these pressures are true only if the pressures are applied gradually.
https://www.google.com/search?q=3/4...e..69i57j0.26044j0j7&sourceid=chrome&ie=UTF-8
In the case of a firearm, the pressure is applied almost instantly. Because of this, the pressures mentioned above do not apply and a pressure far below the burst pressure I mentioned will cause the pipe to fail.
By the way, the pressures in a muzzleloading 12 guage barrel firing black powder can exceed 6000 psi in the breech area. Pressures like that coupled with the fact that they were created by an explosion says to me a 8610 psi burst pressure is far to low to be safe to fire.
Your 3/4" pipe has an internal diameter of about 3/4" and an outside diameter of about 1.050. That results in a wall thickness of .150.
Before the Civil War, the war department ran a number of tests to determine a safe thickness for the wall on a muzzleloading barrel. They arrived at a minimum thickness of .200 in the area of the breech.
If you intend to use the pipe for a barrel I strongly suggest you make the gun impossible to fire.