Any idea of the price of the kit
Steve;First, thanks for the link to the Manton breech plug. The description isn't clear that this consistent of two separate parts (Tang and separate Patent breech?). On the OP build I don't see a definitive "break" for a Manton style BP. Could be there and I just don't see it.
Steve;As for the barrel, again....looking at the Rice site the only other barrel I found that's 31" was a Jaeger Barrel--description is for TOTW--However the measurements are close, but the center is not .375. Then again, this barrel is offered from calibers of .45 all the way up to .62.