Congrats on having a nice 1887 Husqvarna Nagant revolver! It is the best black powder revolver I have ever shot (way better than Colts, Remingtons, S&Ws, etc.), regarding freedom from cylinder binding with repeated shots and long-term small groups. With proper BP loads, it matches ballistics for USA 32-20 in 4-5 inch barreled revolvers (such as S&W Hand Ejector, Colt Police) -- I get 770 fps with 118 grain, nearly pure lead 32-20 bullets. With nitro (smokeless loads) it provides much weaker ballistics, thanks to combination of largish cylinder-barrel gap (typical of excellent BP revolvers) and long throat.
The 7,5 Nagant is pretty much a handloading proposition, IF you want proper ammo. 7,5 Nagant rounds for Swiss and French Ordnance Revolvers apparently are good fit and may be found, even though not loaded for long time. Proper sized cases can be made from USA 32-20 brass.
Many folks shoot 32 S&W longs or shorts, even 32 H&R Mag!, or 32 ACP ammo, the latter in special cylinders chambered for this little cartridge. Only 32-20 cases are a close match for 7,5 Nagant, as regards rims and heads, but are longer -- I fireform them and use them full length with 0,315 or 0,314 bullets soft or pure lead bullets, other shorten them and use 100+ grains, 0,320 healed bullets. I find that Speer 98 grain Hollow base wad cutter bullets work well with various nitro powders, although I have not yet attained same velocities as with black powder (I use Hodgden 777 FFg). I use an 8 mm Lee Factory crimp tool to crimp the 32-20 cases onto the undersized bullets. Bore of my 7,5 Nagant is close to 0,320, as measured on recovered Speer HBWC bullets.
32 S&W shorts and longs are undersized for the back end of the chamber, resulting in buldged cases and poor gas sealing. 32 H&R mag lead bullet loads have same problem. Norma lists 15.000 psi as max operating pressure for 7,5 Nagant. Even in properly chambered guns 32 S&W rounds are held to less than this and 32 H&R lead bullet loads are lower pressure than the jacketed bullet loads (about 21.000 psi). Poor sealing of chamber, large barrel-cylinder gap and long throat of 1887 Swedish Nagant, as well as undersized bullets, reduce actual chamber pressures even more for these ill-fitting rounds.
Like most military double-action revolvers, the hammer spring is stout. I had my gun worked over by a good pistol smith and use Federal small pistol mag match primers (soft primer cups) and get excellent double and single action trigger pulls and totally reliable ignition. Looks like 3-4 inch 6-shot groups at 50 meters may be attainable. I shoot mine in action-shooting matches and it easily goes 7-8 cylinders full (6 rounds) of BP loads with cylinder still turning easily and bullets hitting where I aim. FYI, the gun has a rebounding hammer, allowing loading 6 rounds. Only bummer with this military revolver for action-pistol shooting is that the chambers must be emptied and reloaded one round at a time, as with single-action only revolvers.
Further questions are welcome,