That velocity does not sound extremely reasonable with that case. Besides the older M91/30 Nagants with the longer barrels tend to be the more fragile Nagant's. I've heard to not even use current production 7.62x54R in them because pressure is too high. I can't speak for your rifle but I'd be concerned. The updated Nagant carbines can handle slightly more pressure I believe, enough to safely fire current production ammo.
I'd guestimate that you could push a heavy-ish 181 grain to a MV of around 2800fps if you're lucky.