The .38-55 Ballard & Marlin is often considered tricky to handload for and I suppose it is with the many variations in groove diameter and chamber length but once a good load has been obtained, with perseverence, it's a dandy calibre. I have been happy with such a load in this rifle...
Of all the medium burning rate powders in these large straight walled cases I have enjoyed I.M.R. 4198 and in this rifle 19.0 grains with a compressible filler of Dacron between the bullet and powder has given me the most consistent results. This target was shot at 50 yards from a sandbag rest with a chronographed speed of 1400 f.p.s. which is in keeping with it's blackpowder equivalent.
The rifle slugs to .376" and I use the Lee flat nose/ flat base 255 grain bullet which falls from the mould at .380"/.381" but sized to .379" with a push through sizer, which I prefer. I use the R.C.B.S. Cowboy Action dies with a .379" expander. I trim the cases to 2.056" and with an O.A. Length of 2.322" the bullet is just short of the lands. I have had no leading with Lee's Alox tumble lube. I push the Dacron filler in with a small brass rod until it is compressible and eliminates all the air space. I think this filler allows for better burning characteristics and eliminates powder sensitivity even with I.M.R.4198 which isn't supposed to exhibit much.
Thanks.