I'm guessing 1:22", I get around 1 revolution running a patch through the 26" barrel (23.5" of rifling). So far I've only shot 550 grain flat nosed through it and it's pretty lively on the back end. If I plan on shooting more than a couple rounds I have to put a pussy pad over that steel carbine butplate to keep my shoulder from turning pretty colors. I'd be afeared to throw a 700 grainer out of it like you do yours!
