bb - SMI converts their barrels the same way that "...(the GBO) member has installed many of the Savage smokeless BPs in 45-70 Handis." does. I compared the one SMI makes, against the one I had it done by the GBO member. They are the same, except, for the following:
1)I had the newer Savage BP, which could be removed with 5/8" standard socket, and the one SMI supplied to a GBO member needed some tool to remove it. The current ones made by SMI also use the new Savage BP.
2)The SMI version, comes with a 5 piece takedown ramrod, and the one made by the GBO member has a telescoping ram rod, similar to the H&R ramrod, but IMHO a lot sturdier.
3)The barrel made by SMI, does not have any ramrod thimbles, the one made by the GBO member does.