Chasseur and Rusty,
It is paramont that one uses a good gob of filler with IMR-3031 or you will build pressures as there is simply too much space in the big cases, thats a given...

Before the advent of some of the newer powders like 4831, 4350,RLs, IMR-3031 was the powder of choice for all doubles and for many years the only available powder that would work with them.

As too this barrel thing I am very anxious to see Rustys gun, and he should have the steel ex-rayed and have some testing done...I have talked to many of the double rifle gunsmiths and those I have talked to tell me this cannot take place and it it did then the rifleing would be very shallow on the inside indeed as the would be pushed out and copper, brass being softer than steel makes this an impossiblity..the gun would have to be a smooth bore because the metal must go somewhere and if it goes out, then it cannot remain in...makes since to me...

I strongly suspect that what Rusty is seeing is perhaps the remements of a hammer forged barrel, the rigdes caused in turning the barrel down and polishing or something on that order, but should he be correct he will certainly get a check from me and my search for the truth will finally come to an end, but I have been at this point before and nothing came of it...

I would love to see that gun studied by someone like L&L Interprises or even Whites laboratories, as I have a lot of respect for Rusty and some of that group when it comes to double rifles...