Quiet, you. This is hogwash.
Have to agree this time.
The issue isn't likely to be the twist. Someone up-thread mentioned Marlins in .44 and .45 having a tight spot under the rear sight dovetail. If this is the case, it's much like some Rugers that had a constriction at the forcing cone. The answer to the problem is fire lapping. My personal preference is LBT's fire lapping kit but Wheeler Engineering's kit (available through Midway) works well, too. You need to start with over-diameter lead bullets .. bigger than the largest part of the bore. I'd go with 5-6 bullets with each grit in the Wheeler kit or 12-15 bullets with LBT's whch has only 1 grit. Afterwards, shoot some jacketed bullets to polish the freshly cut steel.
Just like with a revolver, when you're done, you're likely to have a slightly tapered bore. Match the bullet to bore diameter at the breech, then add a half a thousandth to a thousandth inch diameter. Yep, you're probably going to have to cast your own. I've had .44 carbines with a 1-38" twist handle 300s just fine, but you can hedge your bet a little if you go around 270 to 280 grains and have the crimp groove cut for SAAMI max length, not revolver length, else it they probably won't feet. I'd be inclined to go with an LFN, not a WFN, for a carbine.
Just my opinion of course.
Tom
