The Rock Chuck is a Special Forces assault rifle with a built-in suppressor that never wears out. You unlock it by clearing every Marauder Camp. It is the best gun in the game for quiet kills at any range.
Find and clear every Marauder Camp. When the storyline hits 100%, the rifle goes into your weapon locker.
It lets you clear camps and Infestation zones without alerting the area. You can follow a silent headshot with full-auto fire if things go wrong.
The crossbows are silent but slow to reload. Oil filter suppressors wear out. The Rock Chuck has neither problem, though it hits lighter than unsuppressed rifles.
.22 Repeater
The .22 Repeater is a Poor-condition primary rifle you unlock at Tucker's Hot Springs camp. It fires fast and its ammo is everywhere, but each shot hits soft. Use it for early Swarmer packs, then replace it.
Badlands Big Game
The Badlands Big Game is a Special Forces lever-action rifle for the primary slot. It reloads slowly, but every shot is accurate and heavy. It is a strong pick if you like to fight humans and big Freakers from range.
IDF Pup
The IDF Pup is a Special Forces bullpup rifle you get free for clearing Hordes. It unlocks at 50% of Horde Killer with a 45-round magazine. It is accurate, fast and one of the best primaries for Horde fights.
M14
The M14 is an Average-condition semi-automatic rifle sold at Lost Lake from Trust level 1. It fires quickly and accurately, which makes it good for picking off targets at a distance. An extended magazine takes it from 10 to 16 rounds.