I have a recenty acquired a Winchester 1873 in 44-40, manufactured in 1890. Grooves measure .4255. Lands measure: .433. The chamber measures to .44 or larger. Its not perfectly round, so on my chamber casting, the .444 was the narrowest measurement.
I just bought hollow base, .429, 222 grain bullets from buffalo arms. They are loaded up, but I haven't made it to the range yet. I'm trying to find better options. I've found a mold: accurate 43-210b 210 grain. I've read that if you use soft enough lead that it can obturate and fill the grooves. Sounds ambtious. Looking for suggestions