just a tip from experience learned, size cast bullets at least .001 larger than bore diameter,
most pistol caliber carbines are reasonably accurate with typical copper jacketed 225-260 grain bullets,
but I vastly prefer the increased penetration, and far lower cost of heavy cast bullets,
in the 290-310 grain weight range.(but they (310 grain in 44 mag) (300 grain in 45 colt)
https://www.midsouthshooterssupply.c...ld-c452-300-rf
must be sized, lubed and loaded to near top velocity)
before you purchase a 45 colt or 44 mag lever action ,check the rifles twist rate
I've hunted with a marlin 44 mag 1894 for 4 decades, in every case I tested the faster twist rates seem to work better with cast bullet designs
my rifles very accurate with heavy cast bullets but only at near max velocity,
and the twist rate is barely adequate to keep the preferred 310 grain hard cast bullets stable
you need a full 21 grain charge of H110 powder

https://www.midsouthshooterssupply.c...ld-c430-310-rf
twist rates near 1/20 are much preferred , for better stability,
over slower twist rates in the 1/36 range and the rifles came with both/either,
twist rates at various times over the last few decades