You will need to rank up to at least Level 19 to receive enough diamonds to unlock all weapons ( higher if you have reset your diamonds at any point )
To make things a little easier, I've listed the number of weapon kills (Maintenance Manual) , executions (Operations Manual) & headshot/ Multikills (Bandoliers) you will need to achieve, in the same order as that found on the in-game Player Statistics page, and also included the class and level for each weapon.
Weapon______Class__Lvl__ Kills __Exec__ H/S__ M/K
Makarov______Shrp___1___100____ 50___ 50___ 0
6P9____________Sab___1___100_____50___ 50___0
Star .45_______Com___1___300___200__ 100___0
Eagle.50______Gun____1__ 300 ___200__ 100__ 0
MAC-10_______Guer___1__100____ 50___ 50___ 0
Uzi____________Rbl_____2__ 250__ 100___ 100__ 0
Flare Pistol ___Shrp___2__ 100____0______ 0___ 0
IED___________Guer___2___ 0_____ 0______ 0___ 100
M-79__________Com___2___ 100___ 0______0____100
G3-KA4_______Com___1____100___ 50____ 50___ 0
Silent MP-5____Sab___2___ 100___ 50____ 50___ 0
AK-47_________Com___2___ 250__ 100___ 100__ 0
AR-16_________Sab____3___ 250__ 100___ 100___0
FAL PARA._____Com___3___ 500__ 250___250__ 0
Homeland 37__Guer__1____100___50___ 50___ 0
SPAS-12_______Guer___2___ 250__100__ 100__ 0
USAS-12_______Guer___3___ 500__ 250__ 250__ 0
M1903_________Shrp___1___100___50____50___ 0
Dragunov SVD__Shrp__2__ 250___100__ 100__ 0
AS50___________Shrp___3__ 500___250___250__ 0
Dart Rifle_______Sab___1___250___100___100__ 0
PKM____________Gun___1___250___100___100__0
M-249__________Gun___3__ 500___250___250__ 0
LPO-50_________Rbl____1___ 250___ 0____ 0_____ 0
RPG-7__________Rbl____2___ 100___ 0 ____0____100
Carl-G__________Gun___2 ___250___ 0____ 0___ 100
MGL-140_______Rbl____3___ 500___ 0____ 0___ 250
Good Luck.
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Edit: According to
Timutimu the Carl-G multikills is meant to be 200, I can't recall as it was a long time ago now, funny that
no-one else picked up on it.
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2nd Edit : I've changed Carl-G back to 100 multi-kills after several people have reconfirmed what I had originally. Thanks guys.