I haven't shot a 38-55, but have a tad of experience with two of my Dad's RB's in .43 Spanish. One was a rifle, the other a carbine.
I was only able to try a few rounds of smokeless (all he had prepared).....Trailboss I believe....anyway, the loads were very nice for offhand and plinking & we were getting lots of hits offhand at around 100 yds on my steel plates (roughly 11" x 14")....this was another of the rifles my son was able to shoot during our last outing.
Regards,
Slim