This is the start of the 3rd season for me with the 38-56 and it has been a struggle up to now. If you send me an Australian $20 gold-piece I'll tell you all my secrets.
First, I only shoot fixed ammo.
After many different bullet/load mixes have found two (2) bullets that are working well at longer distances. They are the 330gr Lyman and the 325gr BACo. Have done most of my shooting this year with the 325gr bullet and 56gr of 1.5F Swiss, using three wads (2x 0.060" & 1x 0.030" fiber) to get the bullet spaced out into the lands. Both Starline and Rem cases resized to 38-56. Rem LR primers and, essentially no compression. Drop-tube the powder, thumb in the first wad and seat onto the powder using a pencil and then the next two wads the same way. Thumb-seat the bullet. No compression to speak of and no neck tension. I do not touch the brass after it has been fire-formed. SPG lube.
My experience has been that more powder and compression leads to worse performance on the target, which is sort of the general rule for BP bottleneck cases. I've never tried more than 61gr as everything I've tried above 58gr has opened up the groups.
At our mid-range match the end of last month this load, in a 32" long full octagon Green Mountain 14" twist barrel in a C. Sharps High Wall SST shot a 98-2x at 200yd, 78 at 300yd (after the dumbass shooter threw away two shots - a 5 & a miss) and an 84 at 600yd (where the same da shooter needs to learn a consistent hold). So, am optimistic that this load can be refined into something that is competitive.
Can you post a pic of your bullet and tell us more about it (weight, length, diameter of the bands, etc.) and a pic of your chamber cast? Have you slugged the bore? If so, what are the results.
Has been a bit of a trial to get to this point, but I was new to BP when I started, and have learned a great deal in the past couple of years. Both here and on the Shiloh Sharps forum, and especially from folks at the various competitions.