Re: 9 mm Nagant M '1877
Wow! Now that's a rare one.
I can't help with specifics on the pistol itself, since I've only seen em in pictures.
But the bit of info I have in one of my books on the 9mm Belgian (aka 9.4 Bachmann or 9.4mm Nagant) is a 12gram lead round nose over 1gram of black powder giving 195meters/sec. I don't have any SAE spec data, case dimensions, or other info to offer.
Remember, this will be a black-powder-only affair since that thing was designed before smokeless powder.
Do you have a source for brass and bullets?