LongWalker, if I were to use a filler, would the added weight cause a substantial increase in recoil? I have a 54 cal that doesn't seem to rock my boat too bad. I can't believe the filler would increase the recoil more than using 95 grains in that 54.
Saw your post today and had to go dig out my notes.
Back in 2013 I borrowed an original Dickert for some shooting tests. The bore was about .49 caliber (slugged .484" across the lands), with about an inch of bad erosion at the breech that over 2" or so gradually transitioned to just being frosted. When the rifle was later sold, the new owner had it freshed out. To clean up the breech, the guy who did the work had to take it out to .52 caliber.
When I shot the rifle with the original bore, I did my test shooting using a charges that averaged around 80 grains FFg depending on powder brand and lot. Patching was linen lubed with neatsfoot oil, mic'ing .014". Ball diameter was around .469" (antique mould that didn't cast a perfect sphere). This left the patched ball in a fairly rough area of the bore, and many of my patches reflected this.
After my original tests I did some fairly extensive shooting of the rifle. One of the tests was using cream of wheat as a filler to move the ball forward to a smoother area of the bore. I used a powder flask that threw a dram (~27 grains) of powder to meter the filler. My notes mention that the POI moved but no change in accuracy, and that the patches generally weren't torn up. I didn't notice any change in recoil, or I'd have noted it.
I know how bothersome a rough bore and torn patches can be, but in fairness I should point out that in my original tests with this rifle I averaged ~75% for hits on an IPSC silhouette at 200 yards, and ~50% at 300 yards. Granted, the rifle shoots better now, but it wasn't too shabby with a rough bore. (And honestly, I suspect the new crown had more of an effect on accuracy than the bore being freshed.)