Grumpy-
Not too long ago, after almost 40 years of reloading "normal" cartridges, I acquired a 44-40 simply because I fell in love with a Uberti 1866 Sporting Rifle that was chambered therein. A couple of original '73 Winchesters in 38-40 followed shortly thereafter.
I'd read for some time the horror and difficulty experienced by many when reloading these cartridges. Having reloaded all manner of cartridges since I was a young teenager, I couldn't figure out what could be so difficult about the xx-40 cartridges and wrote it off to drama.
When folks here refer to the bore diameter of their firearms, they actually mean
groove diameter. I've owned exactly four .44 caliber Uberti lever rifles in 44-40, .44 Special, and .44 Magnum and they all had groove diameters of .429". Since I already cast for a few .44 Specials and a .44 Magnum and size their bullets .430" my 44-40 bullets got the same treatment and fed like the proverbial $h1t through a goose, in two different 44-40's. As with
any rifle cartridge whose bullet needs to be crimped in place, case length is very important and ensuring your cases are trimmed the same length will likely head off any problems.
I bet you're going to have fun with your rifle. I've loaded smokeless and BP and enjoy both, although smokeless is more simple to load and efficient.
I'm Jones-ing for an 1866 carbine in 44-40 as I enjoy hunting with this caliber, maybe later this year.
CHT