This is probably a stupid question but I am fixing to order a barrel blank for the trapdoor project, and I must ask, as I have never owned a 38-55 what twist rate should I get?  I have decided on a kreiger and they give me plenty of options but I have no idea where to start.  - was thinking 1 in 12 but I know very little about these things.  I am planning to shoot the heaviest bullets I can get my hands on.

My 38/55 is a 16 twist and stabilizes 300 grain bullets very well. I doubt if it will stabilize longer bullets.  It has preformed very well at 500 yards

When you go faster twist and heavier bullets the rifle gets to be more specialized, If long is the way it's going to be shot that's the way to go.  200 yard Schuetzen a slower twist  and bullet around 300 is the way to go. Good performance, less recoil, not real fussy about the way it's loaded. 

If you plan to use Black powder the 38/55 case capacity tends to limit bullet weight anyway.  For true long might look to one of the larger 38 cases.

Boats