Mosins seem to spawn heavily in industrial areas, for some reason. Scopes can be found in Airfield Control Towers or in the abandoned military camp outside Balota. 7.62 Ammo can be found in any Military loot spawn. The Mosin can hold five 7.62 rounds at a time and doesn't require a magazine (you can also chamber individual rounds, though i haven't found much use for that). What this means is that you can take loose bullets you find on the ground and put them to immediate use, but you have to open your inventory and manually load the next five rounds rather than just pressing the reload button. Personally, with all it's attachments and the ease at which you can find ammo for it, I prefer the M4A1. With a pristine ACOG scope and a bipod, it can be fired with decent mid-long range accuracy. High rate of fire and a sceady hand on the mouse will give you almost semi-auto sniper fire and if your enemy survives to run into mid-close range, you can go full auto and turn him into bullet riddled raspberry jam. Fast reload, with multiple magazines is another reason that the M4A1 is, in my opinion, superior to the Mosin at most ranges. The only time the Mosin outstrips the M4 is at really long range, and unless you are set up in a sniper position where you can't be snuck up on, That's not much of an advantage,