I picked up an old Spanish El Tigre carbine in 44-40 a while back. It was carried a lot in its lifetime but very tight mechanically and a clean bore with almost no pitting. However, the lands are worn from the muzzle to a point about 4 inches into the barrel - I expect this came from careless use of cleaning rods over the years - especially since it had a brass 3 pc rod under the spring tab in the butt plate. The grooves are pretty consistent but I can slide sequential gage pins inside the barrel and observe a "bell-mouth" condition of about .003 max. at the muzzle opening that tapers gradually until reaching a consistent diameter back to the chamber.
I am using John Kort's 43-215C bullet design from Accurate Mold, with different hardness lead and smokeless powder combinations. To date, everything I have tried is running consistently about 3-4" groups at 25 yards from a rest. I have owned several 44-40 rifles since buying my first one in the 1970's and I know the cartridge is capable of much better accuracy. My last '92 Winchester would throw 2" groups at 100 yards if I did my part.
I'm concerned this amount of wear is contributing to the larger than normal groups and that I'll have to switch over to jacketed slugs (don't want to go there). I also thought about fire-lapping but that may cause more harm.
Any constructive suggestions are appreciated...HW