I've Been Playing Warzone and Vanguard Recently and I Found Out That the 3-Line Rifle With The 30.06 20rnd Mags and the Kovalevskaya 820mm R1MN Barrel, do 150+ Damage in Warzone(Instant Shield Crack) and in Vanguard, One Shots to the Head, Torso, Upper Legs and to the Shoulders.

Try it Out for Yourself, I Recommend Pairing With The STG44 for WZ and the Combat Shotgun for Vanguard, But Use Whatever Secondary You Want Too.