I looked at a Nagant in a gun shop a couple of years ago, and it was in such good shape, I thought about getting it... until I picked it up (and after making sure it was unloaded) dry fired the thing. I almost had to put a second finger on the trigger in order to pull it, the DA pull was so heavy. (About a week later, I read an article on one in a gun magazine, the author had the same experience, saying that his first thought was "is it broken?"). The single action trigger was awful as well, but was at least manageable with merely human physical strength.
I will never understand why the Russians ever adopted the Nagant, since at the time they took it into service, they already had a revolver that was markedly superior in every way. When they traded in the S&W revolvers they had adopted in the 1870s for the Nagant, they traded a potent, manstopping cartridge for a pipsqueak one. They traded a break top with automatic ejection, which could be reloaded very quickly, for a revolver that had to have its cartridges loaded one at a time through a loading gate, and ejected, again one at a time, with a rod (and not a spring loaded one either, so it's slower than the one on a Colt SAA). And they traded a revolver with a very good single action pull for one with a horrible one. The only theoretical advantage they gained was with the double action trigger, and since that was so heavy as to render it unusable, it was no gain at all. The gun was surely seldom fired in DA mode. I can't even imagine shooting a revolver accurately with such a heavy DA pull. It surely can't be possible to hit anything beyond point blank range with it; the effort of pulling that nautilus machine-like trigger would inevitably pull one's shot off the point of aim.