Now I got to wondering just how much powder I could squeeze into a spanking new case if I tried compressing it a bit and let the bullet set out. I loaded one round with 20 grains. No problem; lots of room to still set the bullet out. This one gave 692 fps; still mystified about that. Then I loaded 21 grains into a new case. This one round gave me 753 fps. I still had room to set the bullet out a bit more, so I loaded 22 grains of FFFg into three never-fired Starline cases. The bullets were sitting out a bit by now, as you can see in the photo below ...(the one on the left has 22 grains of powder and the one on the right has 18 grains) ...
I fired the three cartridges loaded with 22 grains, just one grain short of the original 23 grains, and chronographed the three bullets at 772 fps, 776 fps, and 791 fps, for an average of 780 fps. I would guess that 23 grains should put me right around 800 fps. Keep in mind, today's shooting was done out of an 8" barrel.
Loading up the old sixgun (my coat doesn't have wings, it was just windy) ....
Making smoke .....
The old sixgun after 15 rounds .... a bit covered in residue. It letters as having been shipped in 1873 ....
The backstop. Although I wasn't really aiming at anything on the block of wood, I was just aiming to shoot between the wires on the chronograph, 10 rounds went into about an inch and a half, with the other 5 rounds close. The wood was about 17 feet away. I find this old S&W, with its 8" barrel, remarkably easy to shoot accurately (at least for an old geezer like myself who is no great shakes with a sixgun).
Cleaning the old S&W afterwards ...
Conclusion: If I can stuff 22 grains of FFFg in spanking new Starline cases, I figure I should be able to put the full 23 grains into the slightly expanded fired cases if I don't do any sizing, which isn't necessary anyway, because the bullets are still a tight fit. I ran out of time to experiment further today, but I will be trying for 23 grains next time.

