Martin,

The bullet and lube you use will make a difference on accuracy and consistency of operation, I'm assuming here you will be using lead bullets

Normal smokeless lubes do not work very well with BP, something like SPG is a very good lube off the shelf, if not you can easy make BP lube.

Also the hardness of the bullet makes a significant difference in BPCR's such as 45-70, 40-65's etc, not familiar with smaller capacity cases like the 44-40, but too hard a bullet and you will not get good accuracy. The BP explodes and 'smacks' the base of the bullet which then obturates into the rifling nicely. Too hard a bullet alloy (such as you find in cast bullets for smokeless) and this does not happen. This is also why and over powder wad is good in BP cartridges.

The choice of primer is more critical with BP, been lots of work carried out re. magnum vs standard, under powder or over primer paper discs/wads but again more related to the larger BPCR calibres.

Brgds Terry