HK Naming Conventions

HK53
A "Ausfuhrung" — version
(A2, A3, etc.) Denotes different variations of a design. HK generally uses this to distinguish between firearms with different stocks. A2 often indicates a fixed stock and A3 a retractable one, though note that this is not the case for the G3. Also, different A numbers can refer to different sights (as in MP5KA1) or trigger group (as in MP5KA4 and MP5KA5).
C Woodland camouflage
E Export
Export version
G "Gewehr" — rifle or gun
Rifle adopted for use or testing by the German military. "G" numbers are assigned by the German military.
    G1 = Fabrique Nationale FAL
    G2 = SIG StG57
    G3 = Heckler & Koch CETME
    G4 = Armalite AR-10
    etc.
HK Heckler & Koch
"HK" numbers work according to the system described below. Note that this only applies to designations of "HK" followed by a number; "G", "MP","P", etc. work differently:
 
First character (tens digit): type of weapon
1Box-fed light machine gun
2Belt-fed machine gun
3Select-fire assault rifle
4Paramilitary rifle (German or early US civilian)
5Submachine gun
6Grenade launcher, complete weapon
7Grenade launcher, add-on weapon
8Police tactical rifle (?)
9Semi-automatic paramilitary rifle (USA)
 
Second character (ones digit): caliber
17.62 x 51 mm NATO (.308)
27.62 x 39 mm Soviet
35.56 x 45 mm NATO (.223 Remington)
49 x 19 mm NATO (9mm Luger)
5.50 BMG (not used)
64.6 x 36 mm
7(not used)
8(not used)
940 mm
K "Kurz" — short
Shortened barrel
M "Militär" — military
Used to distinguish the VP70Z (civilian) from the VP70M (military)
MP "Maschinepistole" — machine pistol)
Submachine gun. "MP" numbers are assigned by the German military for submachine guns they have tested or adopted.
OHWS Offensive Handgun Weapon System
Alternate name for the MK23 SOCOM
P "Pistole" — pistol
Pistol
PSG "Prazisionschützengewehr" — precision shooter's / marksman's rifle
High-precision marksman/sniper version
PSP "Polizei Selbstlade Pistole" — police self-loading pistol
A predecessor of the P7 pistol
S Desert camouflage
SD Supressed
T Target
Specially designed to meet "sporting purpose" restrictions
TC Target Competition
Specially designed to meet "sporting purpose" restrictions
TGS Tactical Group Support
Grenade launcher attached
SG "Scharfschützen Gewehr" — sharpshooter's rifle
or, "Schützengewehr" — shooter's rifle / marksman's rifle
Sniper version
UMP "Universal Machinenpistole" — Universal Submachinegun
A particular HK submachinegun
USP Universal Self-loading Pistol
A particular line of semiautomatic handguns
VP "Volkspistole" — People's Pistol
Name given to the VP70 pistol
Z "Zielfernroh" — telescope
Telescopic sights
Z "Zivilversion" — civilian version
Used to distinguish the VP70Z (civilian) from the VP70M (military)
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