The thing that keeps the Mosin-Nagant going is the cheap availability of spare parts and ammunition. It’s still a very good sniping rifle up to around 400-600 yards range.
I have one that I bought for 80 bucks. I shortened the barrel by about 3 inches, installed an after market fiberglass stock with a monte carlo cheekpiece, did a trigger job and mounted a 2.5 power long eye relief scope where the original rear sights were.
It makes a fine scout type rifle for deer and black bear. The 7.62 X 54 round is quite adequate for most North American game. Kicks like hell though.
A snipers rifle is 7.62X51 to a 1000 meters, .300 Win Mag to 1200 meters, .338 Lapua to 2000 meters. And if you want to just get silly, the crowd pleasing .50 BMG on a 34in. barreled Barrett. If your looking for a old military rifle to a 1000 meters go find a British Enfield .303 in good shape.