A 1:22 twist. I sent a marlin 30-30 barrel to JES and it was returned today with 5 groove rifling. I asked for the same groove/bore as the 405 Win/405JES, 0.412"/0.402". I will slug the barrel then get in touch with Accurate for a mold.
I still need to ream the chamber but the rest of the shotgun is ready. I have built four (4) 336-444 Marlin leverguns so after the chamber is cut a quick barrel swap and I am done, I hope.
I will be loading metal/plastic 410 hulls so the gun will be Ohio deer legal. I am hoping to push a 250g cast boolit at 1,800 fps, a load that would be way too hot for a standard 410, but this ain't a standard 410.
Pics to follow once I get it finished.
BB