Learn how to properly clean the Russian Mosin Nagant bolt action rifle from a professional gunsmith at Brownells. You will need a gun cleaning kit with a long cleaning rod, preferably a 36″ cleaning rod. This gunsmith uses Hoppes No 9 gun solvent but you can use other CLPs or gun cleaners like Weapon Shield, M-Pro7 gun cleaner, Breakfree CLP, Ballistol CLP, Hornady One Shot, etc.
If you have used corrosive surplus ammo or just bought the rifle, I suggest cleaning it as if corrosive ammo was used in it. You must clean it with hot water first to remove the corrosive salts. A great method is to mix Ballistol with warm or hot water and then clean the gun. The Ballistol will clean and prevent corrosion while the water will dissolve the corrosive salt. You can buy Ballistol here.