Noone can deny that the achievement for the Mosin nagant is just garbage because of the tripwire kills.
Here's how to do it in about 2-3 rounds depending how dumb the enemy team is.
1.Sneak behind enemy camper, place tripwire
2.Shoot him in the back and wait for him to move
3.+1 tripwire kill
Also use gas grenades or incendiary to drop their hp so they die when they cross the tripwire wich deals approx 75 dmg now that flak exists as an ability.
I wish you all the best of luck and enjoy the M91