Shotgun Buff:

Shotguns need a slight buff to its current ammo type. Rifled Slugs can do extreme damage in real life, but in game. shot from a rifled slug cannot kill a deer or a zombie. And Buckshot can't kill a Zombie in 1 shot either.
I suggest a new ammo type, 12ga Birdshot.
I also suggest two muzzle attachments, a Choke for the single barreled shotguns. (Helps tighten the pellet spread) and a Box Suppressor (Suppressor designed for Shotguns).

A new improvised Explosive:

Pipe bomb.
Using a Pipe and a Hacksaw, you cut the pipe end pieces off to shorten it to a small pipe. Combine the small pipe and a Electronic Repair Kit to get the Pipe Bomb without the explosive charge. Then using a Plastic Explosive to put it in its explosive slot (Should only have 1 Explosive slot) Then the Pipe Bomb can be used like a grenade.

A New Improvised Suppressor:

A Pipe Suppressor should be implemented, a better version of the bottle suppressor, but this improvised suppressor should only work with guns that have a threaded barrel.

How to Make:
Using a Pipe and a Hacksaw, you cut the pipe end pieces off to shorten it to a small pipe.
Using a pipe wrench, going to a wrecked vehicle engine. We could salvage engine for ball bearings. Up to stack of 10. (Process should take as long as gathering for a worm)
Once having the small pipe and having 10 ball bearings. You combine the two ingredients; you can craft the pipe suppressor. Epoxy Putty should be the repairing item for this suppressor, The durability should be lower than a normalized suppressor but being higher than the bottle suppressor.

A New KA Variant, KA-47:

Chambered in 762x39mm. Change the 30Rnd AKM mag to Normalized 30Rnd Mag, 75Rnd AKM Drum to 75Rnd Normalized Drum but not the polymer mags. Can have KA attachments. This Ka-47 should use the Normalized Mags.
New High Tier Weapons:

New High Tier Weapons:
M14 and MK14 both chambered in 762x54mmR
M14 attachment slots: suppressor (improvised only), ghillie wrap. and 20Rnd M14 Mag.
Mk14 attachments: suppressor (Normalized and Improvised), Ghillie Wrap, 20Rnd M14 Mag, and Western Optics.
M14 has Semi and Full Auto
Mk14 has Semi, Burst, and Full Auto
Mk14 should be deloot, and m14 should be Contaminated loot.

New Mid-Tier Weapon:
M1 Garand should be rarer than a SKS.
Cambered in 308WIN. Internal Feed or Clip Feed

New Mag and Clips:

A 4 Round Mag for the CR550 Savanah should be implemented.
Clips for SKS, Garand, Mosin should be implemented.