Personally I get headaches trying to remember all this crap.
Lets try this!
JLD/PTR-91 FMP Tooling
Heckler & Koch's receiver tooling was also sold to the American company Ohio Rapid Fire, which is in the process of setting up to produce receiver.
Third Party Receivers
Federal Arms
FA91
HK91 clone. 7.62 NATO. US manufacture. Aluminum. Integrated Weaver rail.
FMP
(FMP receiver)
HK91 clone. 7.62 NATO. Portugese manufacture. Stamped steel.
Hellenic Arms
(Hellenic receiver)
HK91 clone. 7.62 NATO. Greek manufacture. Stamped steel. Used in Springfield Armory SAR-3 and SAR-8. (No longer imported?)
Hesse Arms
H91
HK91 clone. 7.62 NATO. US manufacture. Stamped steel.
Special Weapons LLC
SW3
HK91 clone. 7.62 NATO. US manufacture. Cast steel. Rights purchased 1999 by Century Arms.
SW5
HK94 clone. 9mm NATO. Cast steel. US manufacture.
7.62 NATO Semi-Automatic (HK91 Clones)
Century Arms
Centurion 99 Sporter Rifle
HK91 clone. Federal Arms FA91 aluminum receiver. Integrated Weaver rail.
Centurion 99 Sporter Rifle (Century Arms)
Centurion 2000
HK91 clone. Hesse H91 receiver.
Federal Arms
FA91
HK91 clone. Federal Arms aluminum FA91 receiver. Integrated Weaver rail.
FJ Vollmer
HK51 Semi-auto conversion
HK91 converted with MP5 handguard, shorter cocking tube. 16 inch barrel.
FMP
G3/S / G3S
HK91 clone. FMP receiver. (distinguishing traits?)
XG3/S / XG3S
HK91 clone. FMP receiver. (distinguishing traits?)
SLG-95 / SLG95
HK91 clone. FMP receiver. (distinguishing traits?)
Hesse Arms
H91
HK91 clone. Hesse receiver.
H91 Rifle (Hesse Arms)
H91MR (H91 Marksman Rifle)
HK91 clone. Hesse receiver. Strengthening rails welded in. Wide handguard. Adjustable buttstock.
H91 Marksman Rifle (Hesse Arms)
H91PR (H91 Precision Rifle)
HK91 clone. Hesse receiver. Strengthening rails welded in. 26 inch floated barrel. Adjustable buttstock. Target pistol grip.
H91 Precision Rifle (Hesse Arms)
Special Weapons LLC
SW3
HK91 clone. Special Weapons receiver. Rights purchased 1999 by Century Arms.
SW3BF
HK21E clone in semi-auto. Special Weapons receiver. Project on hold.
Springfield Armory
SAR-3
HK91 clone. Hellenic receiver. Fixed or retractable stock, flash hider. Banned from US import 1989.
SAR-8 (old)
HK91 clone. Hellenic receiver. Thumbhole stock. Discontinued.
SAR-8 (new)
HK91 clone. Cast aluminum receiver with integrated Weaver rail. Pistol grip, slim forearm, green furniture. Introduced 1999.
5.56 NATO Semi-Automatic (HK93 Clones)
FJ Vollmer
HK53 Semi-auto conversion
HK93 converted with MP5 handguard, shorter cocking tube. 16 inch barrel.
9mm NATO Semi-Automatic (HK94 Clones)
Special Weapons LLC
SW5
HK94 clone. Special Weapons receiver.
SW5 9mm Sporting Rifle (Special Weapons LLC)
Other Caliber Semi-Automatic
Fleming Firearms
HK92
HK91 rechambered for 7.62x39 Soviet.
Special Weapons LLC
SW12
12-gauge shotgun. Special Weapons receiver. Not yet available.
SW12 12 gauge Shotgun (Special Weapons LLC)
SW45
.45 ACP sporting rifle. Special Weapons receiver. Similar design to HK94.
SW45 45acp Sporting Rifle (Special Weapons LLC)
NFA / LEO 7.62 NATO (G3 / HK51 / HK21 Clones)
FJ Vollmer
Model 21
Belt-fed 7.62 NATO HK21 clone. Also available with PSG1 sniper stock.
Model 21K Machine Pistol
Belt-fed 7.62 NATO pistol with 7 inch barrel, stockless butt plate, quick-change barrel, detachable belt-feed ammunition box from HK21E.
Model 51
HK91 converted to full-auto, 9 inch barrel.
Model 51B
Belt-fed 7.62 NATO, 9 inch barrel, retractable stock, HK53 handguards.
Fleming Firearms
51
HK91 converted to full-auto, 8.9 inch barrel.
51K
HK91 converted to full-auto, 4.7 inch barrel.
G3A2
HK91 converted to full-auto, fixed stock.
G3A3
HK91 converted to full-auto, retractable stock.
G3K
HK91 converted to full-auto, 11.7 inch barrel.
G3SD
HK91 converted to full-auto, with silencer.
G3KSD
HK91 converted to full-auto, short-barreled, with silencer.
HK21K
Belt-fed machine gun with 12-inch barrel and retractable stock.
NFA / LEO 5.56 NATO (HK33 / HK53 Clones)
FJ Vollmer
Model 53
HK93 converted to full-auto, short barrel.
Fleming Firearms
NFA / LEO 9mm (MP5 Clones)
FJ Vollmer
MP5
HK94 converted to full-auto. (MP5A2 = fixed stock, MP5A3 = retractable)
MP5K
SP89 converted to full-auto, "K" handgrip added to make MP5K clone.
Fleming Firearms
MP5
HK94 converted to full-auto. (MP5A2 = fixed stock, MP5A3 = retractable)
MP5K
HK94 converted to full-auto, MP5K configuration. One inch longer than HK's MP5K, but can be changed between Fleming end cap, MP5 fixed stock, or MP5 telescoping stock.
MP5SD
HK94 converted to full-auto, supressed.
Special Weapons LLC
SWA-5
Full-auto, fixed stock MP5A2 clone. Special Weapons receiver.
Police 9mm (Special Weapons LLC)
SW-5 LE
Semi-auto, fixed stock MP5SFA2 clone. Special Weapons receiver. Short or 16 inch barrel available.
Police 9mm (Special Weapons LLC)
SWA-5-C
Full-auto, retractable stock MP5A3 clone. Special Weapons receiver.
Police 9mm (Special Weapons LLC)
SW-5-C LE
Semi-auto, retractable stock MP5SFA3 clone. Special Weapons receiver. Short or 16 inch barrel available.
Police 9mm (Special Weapons LLC)
SWA-5-P
Full-auto, stockless MP5K clone. Special Weapons receiver.
Police 9mm (Special Weapons LLC)
SW-5-P LE
Semi-auto, stockless MP5K clone. Special Weapons receiver.
Police 9mm (Special Weapons LLC)
SWA-5-K
Full-auto, folding stock MP5K-PDW clone. Special Weapons receiver.
Police 9mm (Special Weapons LLC)
SW-5-K
Semi-auto, folding stock MP5K-PDW clone. Special Weapons receiver.
Police 9mm (Special Weapons LLC)
NFA / LEO Other Caliber
Special Weapons LLC
SWA-45
Full-auto, fixed stock, similar to MP5A2. Special Weapons receiver.
Police (Special Weapons LLC)
SW-45 LE
Semi-auto, fixed stock, similar to MP5SFA2. Special Weapons receiver. Short or 16 inch barrel available.
Police (Special Weapons LLC)
SWA-45-C
Full-auto, retractable stock, similar to MP5A3. Special Weapons receiver.
Police (Special Weapons LLC)
SW-45-C LE
Semi-auto, retractable stock, similar to MP5SFA3. Special Weapons receiver. Short or 16 inch barrel available.
Police (Special Weapons LLC)
SWA-45-P
Full-auto, stockless, similar to MP5K. Special Weapons receiver.
Police (Special Weapons LLC)
SW-45-P LE
Semi-auto, stockless, similar to MP5K. Special Weapons receiver.
Police (Special Weapons LLC)
SWA-45-K
Full-auto, folding stock, similar to MP5K-PDW. Special Weapons receiver.
Police (Special Weapons LLC)
SW-45-K
Semi-auto, folding stock, similar to MP5K-PDW. Special Weapons receiver.
Police (Special Weapons LLC)