Last summer I loaded up some .44 Special with Pyrodex P and .433 round balls. I think I used about 25 grains. I put two cylinderfuls of that into paper at 25 yards from a rest, using an S&W 624. Then I did the same with a Pietta 1858 Remington replica (with .454 balls). I couldn't tell the difference in the groups. Each twelve shots in about 2.5 inches.
When finished, the 624 looked like it had been stored for a year in a bucket of soot. The low pressure Pyrodex cartridges do not obturate well, so the soot goes everywhere. Interesting, but not going to do it again. The 1858 Remington is great, however.