edmelott said:
Also wondering about brass. Would a brass bolt hold up as a touch hole liner?
Brass would work but not for long.
Several things brass isn't good at are corrosion and resistance to high temperatures.
The flame passing thru the vent hole is far higher than the melting point of brass and the fouling remaining following the shot will begin to corrode the hole.
There are several copper based alloys that will work nicely for both vent liners and percussion nipples but they are proprietary and are owned by Ampco.
The Ampco bronze is resistant to hot gas corrosion but it is totally different than a common brass or bronze. It is also hardenable which makes it suitable for percussion nipples.
The stainless steels are the best choice for a vent liner.
They have a high melting point and the nickle and chrome in them resists heat and corrosion.
Both the magnetic and the non-magnetic stainless steels will work nicely for a vent liner.
The non-magnetic stainless steels won't work for percussion nipples though. They cannot be hardened by any process except for work hardening.
There are a number of other alloys that would be excellent for vent liners. These alloys are used in jet engines and are not only resistant to extremely high temperatures and corrosion but they are strong as well.
Among these are the various Inconels, Waspalloy, Rene 41, Hastelloy and other strange names most people never heard of.
The problem with all of them is they are extremely costly and very difficult to machine.