Use the Pack-A-Punch machine to make the following upgrades.

Assault rifles
AUG: AUG-50M3
Commando: Predator
Famas: G16-GL35
FN FAL: EPC WN
G11: G115 Generator
Galil: Lemantation
M14: Mnesia
M16: SkullCrusher

Handguns
CZ75: Calamity
CZ75 Dual Wield: Calamity & Jane
M1911: Mustang & Sally
Python: Cobra

Launchers
China Lake: China Beach
M72 LAW: M72 Anarchy

Light machine guns
HK21: H115 Oscillator
RPK: R115 Resonator

Shotguns
HS10: Typhoid & Mary
Olympia: Hades
SPAZ-12: SPAZ-24
Stakeout: Raid

Sniper rifles
Dragunov: D115 Disassembler
L96A1: L115 Isolator

Submachine guns
AK47u: AK74fu2
MP40: The Afterburner
MPK5: MP115 Kollider
MPL: MPL-LF
PM63: Tokyo & Rose

Special weapons
Ballistic Knife: The Krause Refibrillator
Crossbow: Awful Lawton
Ray Gun: Porter's X2 Ray Gun
Thundergun: Zeus Cannon
Winter's Fury: Winter's Fury