I'm certain it's been done before, but for anyone curious:
After poking around online and mulling it over a while I decided to try a BP load for a semi auto (At least, a recoil operated pistol.)
I used Pyrodex "P"- I filled them almost to the brim, which turned out to be 9.2 grains. I figured the seating of the bullet should pack the load sufficiently.
Made 5, cycled and shot just fine. Of course, lots of soot, I just wish I had a girlfriend as dirty as the gun is right now. :-p
Pistol used: Beretta 92G (Some French army variant where they made the safety into a decocker.)
Bullets seated: Lee roundnoses from the TL356-124-2R. Actual weight was about 123 grains.
Cartridge OAL- 1.150"