I just picked up a very nice Pedersoli Walker at a local pawn shop yesterday, and have been giving it good workout. The chambers hold around 60 grains level full, but Goex 3F is about impossible to compress enough at that level to get the ball into the chamber. Fifty five grains works well. Using American Pioneer, sixty grains is no problem at all. Just for the hell of it, I even compressed the AP in two stages and could still easily seat a round ball with 65 grains. I'm not so sure that 70 grains is out of the question, but I'm quite sure that combustion efficiency vs. velocity gain at these levels probably isn't worth the extra effort. Compared to Goex 3F, American Pioneer gives me noticably less BOOM, the same or even more smoke, and virtually no fouling. I put sixty shots through it this morning with 55 grains AP and the cylinder still turned as well on shot #60 as on shot #1. I found that Pyrodex P had a noticable ignition delay, even when using CCI #11 magnum caps. With all three powders, either flavor of CCI caps could be counted on to not go bang on two out of four chambers on the first hammer strike, and not the same two every time either (Yes, they are definitely #11's). Harder/thicker caps? Oversize/peened nipples? I dunno, but when I switched to Remington #11's, there were no more problems.
Recoil is negligible, kind of like light Bullseye .38 spl target loads, and accuracy is great. My first six shots consisted of 55 grains of Pyrodex P fired at a 3" square Post-It note at 25 yards with a 6 o'clock hold. Upon inspection, I found 5 holes in the square and the sixth only a quarter inch off the left side. Most groups with all three powders have been 2 1/2" or less, center to center, for six shots. I like it!