Successfully complete the indicated task to unlock the corresponding weapon or weapon attachment:

Bolt Action Rifles

Springfield: Reach Level 4.
Bayonet: Successfully complete Marksman Challenge 1 (increases melee attack range).
Rifle Grenade: Successfully complete Marksman Challenge 2 (grenade launcher attachment, replaces Perk 1 slot).
Arisaka: Reach Level 4.
Sniper Scope: Successfully complete Marksman Challenge 1 (increases accuracy and range).
Bayonet: Successfully complete Marksman Challenge 2 (increases melee attack range).
Rifle Grenade: Successfully complete Marksman Challenge 3 (grenade launcher attachment, replaces Perk 1 slot).
Mosin-Nagant: Reach Level 21.
Kar98k: Reach Level 41.
PTRS-41: Reach Level 57.

Rifles

SVT-40: Reach Level 4.
Flash Hider: Successfully complete Marksman Challenge 1 (invisible on radar when firing, reduced muzzle flash, but shorter range).
Aperture Sight: Successfully complete Marksman Challenge 2 (precision sight).
Telescopic Sight: Successfully complete Marksman Challenge 3 (enhanced telescopic sight).
Gewehr 43: Reach Level 7.
Suppressor: Successfully complete Marksman Challenge 1 (invisible on radar when firing, reduced muzzle flash, but shorter range).
Aperture Sight: Successfully complete Marksman Challenge 2 (precision sight).
Telescopic Sight: Successfully complete Marksman Challenge 3 (enhanced telescopic sight).
Rifle Grenade: Successfully complete Marksman Challenge 4 (grenade launcher attachment, replaces Perk 1 slot).
M1 Garand: Reach Level 17.
STG-44: Reach Level 37.
M1A1 Carbine Reach Level 65.

Sub Machine Guns

Thompson: Reach Level 4.
Suppressor: Successfully complete Marksman Challenge 1 (invisible on radar when firing, reduced muzzle flash, but shorter range).
Aperture Sight: Successfully complete Marksman Challenge 2 (precision sight).
Round Drum: Successfully complete Marksman Challenge 3 (increased ammunition capacity).
MP40: Reach Level 10
Suppressor: Successfully complete Marksman Challenge 1 (invisible on radar when firing, reduced muzzle flash, but shorter range).
Aperture Sight: Successfully complete Marksman Challenge 2 (precision sight).
Dual Magazine: Successfully complete Marksman Challenge 3 (increased ammunition capacity).
Type 100: Reach Level 25.
Ppsh: Reach Level 41.

Shotguns

M1897 Trench Gun: Reach Level 4.
Grip: Successfully complete Marksman Challenge 1 (vertical foregrip to reduce recoil, replaces Perk slot 1).
Bayonet: Successfully complete Marksman Challenge 2 (increases melee attack range).
Double Barreled Shotgun: Reach Level 29.

Machine Guns

Type 99: Reach Level 4.
Bipod: Successfully complete Marksman Challenge 1 (reduces motion for more accuracy).
Bayonet: Successfully complete Marksman Challenge 2 (increases melee attack range).
BAR: Reach Level 4.
Bipod: Successfully complete Marksman Challenge 1 (reduces motion for more accuracy).
DP-28: Reach Level 13.
MG 42: Reach Level 33.
FG 42: Reach Level 45.
Browning M1919: Reach Level 61.

Pistols

Colt M1911: Reach Level 4.
Nambu: Reach Level 4.
Walther P38: Reach Level 4.
Tokrev TT-33: Reach Level 21.
.357 Magnum: Reach Level 49.

Primary Grenades

Frag: Reach Level 4.
N 74 ST: Reach Level 4.
Molotov Cocktail: Reach Level 10.

Special Grenades

Smoke: Reach Level 4.
Tabun Gas: Reach Level 4.
Signal Flare: Reach Level 4.