In Escape from Tarkov, the handling of weapons can be trained through active use. In short, the more you use a certain weapon, the more skilled you become with it.
Depending on the weapon, reaching mastery level 2 or level 3 will provide a new reload animation. Level 3 grants the ability to reload while aiming down sights for all weapons in that mastery category.
Weapons that are based on the same platform share a mastery. 1 EXP is gained for every hit on entities in an online raid. For cartridges that fire multiple projectiles, each projectile hit gives EXP.
Assault rifles
Required EXP for level 2: 1600
Required EXP for level 3: 2000
ADAR 2-15 5.56x45 carbine
Colt M4A1 5.56x45 assault rifle
HK 416A5 5.56x45 assault rifle
Required EXP for level 2: 2000
Required EXP for level 3: 2200
Kalashnikov AK-12 5.45x39 assault rifle
Kalashnikov AK-101 5.56x45 assault rifle
Kalashnikov AK-102 5.56x45 assault rifle
Kalashnikov AK-103 7.62x39 assault rifle
Kalashnikov AK-104 7.62x39 assault rifle
Kalashnikov AK-105 5.45x39 assault rifle
Kalashnikov AK-74 5.45x39 assault rifle
Kalashnikov AK-74M 5.45x39 assault rifle
Kalashnikov AK-74N 5.45x39 assault rifle
Kalashnikov AKS-74 5.45x39 assault rifle
Kalashnikov AKS-74N 5.45x39 assault rifle
Rifle Dynamics RD-704 7.62x39 assault rifle
RPK-16 5.45x39 light machine gun
SAG AK-545 5.45x39 carbine
Required EXP for level 2: 500
Required EXP for level 3: 600
Kalashnikov AKM 7.62x39 assault rifle
Kalashnikov AKMN 7.62x39 assault rifle
Kalashnikov AKMS 7.62x39 assault rifle
Kalashnikov AKMSN 7.62x39 assault rifle
Molot Arms VPO-209 .366 TKM carbine
Required EXP for level 2: 275
Required EXP for level 3: 350
Kalashnikov AKS-74U 5.45x39 assault rifle
Kalashnikov AKS-74UB 5.45x39 assault rifle
Required EXP for level 2: 275
Required EXP for level 3: 500
AS VAL 9x39 special assault rifle
Required EXP for level 2: 350
Required EXP for level 3: 500
Steyr AUG A1 5.56x45 assault rifle
Required EXP for level 2: 450
Required EXP for level 3: 600
Desert Tech MDR 5.56x45 assault rifle
Required EXP for level 2: 350
Required EXP for level 3: 500
FN SCAR-L 5.56x45 assault rifle
FN SCAR-L 5.56x45 assault rifle (FDE)
FN SCAR-H 7.62x51 assault rifle
Assault carbines
Required EXP for level 2: 200
Required EXP for level 3: 250
Tokarev AVT-40 7.62x54R automatic rifle
Required EXP for level 2: 200
Required EXP for level 3: 300
Molot Arms Simonov OP-SKS 7.62x39 carbine
Required EXP for level 2: 75
Required EXP for level 3: 150
Required EXP for level 2: 275
Required EXP for level 3: 500
KBP 9A-91 9x39 compact assault rifle
Light machine guns
Required EXP for level 2: 150
Required EXP for level 3: 200
Kalashnikov PKM 7.62x54R machine gun
Required EXP for level 2: 150
Required EXP for level 3: 200
Degtyarev RPD 7.62x39 machine gun
Submachine guns
Required EXP for level 2: 300
Required EXP for level 3: 450
TDI KRISS Vector Gen.2 9x19 submachine gun
Required EXP for level 2: 200
Required EXP for level 3: 250
HK MP5K 9x19 submachine gun
Required EXP for level 2: 550
Required EXP for level 3: 800
HK MP7A1 4.6x30 submachine gun
Required EXP for level 2: 150
Required EXP for level 3: 175
B&T MP9 9x19 submachine gun
Required EXP for level 2: 175
Required EXP for level 3: 350
PP-19-01 "Vityaz" 9x19 submachine gun
Required EXP for level 2: 175
Required EXP for level 3: 200
PP-91-01 "Kedr-B" 9x18PM submachine gun
PP-91 "Kedr" 9x18PM submachine gun
Shotguns
Required EXP for level 2: 350
Required EXP for level 3: 450
Required EXP for level 2: 400
Required EXP for level 3: 800
Required EXP for level 2: 1500
Required EXP for level 3: 2200
MP-153 12ga semi-automatic shotgun
Required EXP for level 2: 150
Required EXP for level 3: 250
MP-43 12ga sawed-off double-barrel shotgun
Required EXP for level 2: 300
Required EXP for level 3: 650
Designated marksman rifles
Required EXP for level 2: 100
Required EXP for level 3: 200
Required EXP for level 2: 175
Required EXP for level 3: 300
Required EXP for level 2: 350
Required EXP for level 3: 300
Required EXP for level 2: 275
Required EXP for level 3: 500
VSS Vintorez 9x39 special sniper rifle
Bolt-action rifles
Required EXP for level 2: 150
Required EXP for level 3: 200
Required EXP for level 2: 100
Required EXP for level 3: 175
Required EXP for level 2: 150
Required EXP for level 3: 200
Required EXP for level 2: 200
Required EXP for level 3: 250
Mosin 7.62x54R bolt-action rifle (Infantry)
Required EXP for level 2: 75
Required EXP for level 3: 125
Required EXP for level 2: 125
Required EXP for level 3: 250
Pistols
Required EXP for level 2: 75
Required EXP for level 3: 100
Stechkin APS 9x18PM machine pistol
Required EXP for level 2: 100
Required EXP for level 3: 125
Glock 17 9x19 pistol
Glock 18C 9x19 machine pistol
Required EXP for level 2: 75
Required EXP for level 3: 100
Colt M1911A1 .45 ACP pistol
Required EXP for level 2: 75
Required EXP for level 3: 100
Makarov PM 9x18PM pistol
Required EXP for level 2: 75
Required EXP for level 3: 100
TT-33 7.62x25 TT pistol
Revolvers
Required EXP for level 2: 75
Required EXP for level 3: 100
Chiappa Rhino 50DS .357 revolver