Heckler & Koch Product Overview and New nomenclature

Heckler & Koch, Germany, have been renaming their weapon systems. It’s been going on for a while and I’ve been trying to decipher this ever since I saw some of the new HK firearms at Enforce Tac 2017, Germany.

Could there be errors in my list? Yes, there’s no key from Heckler & Koch but I will be happy to correct them, missed conclusions etc. and look forward to input in the comments section below. There are for sure some digits missing that I don’t know (yet).

I have tried to add a lof ot pictures to make this more interesting, and there should be direct links to HK’s Homepage to most if not all firearms.

HK’s new 3 digit system can be found towards the bottom.

The Weapon Systems for Military and Law Enforcement is divided into the following areas.


We will skip the Pistols, Grenade Machine Gun and Training Systems this time and focus on the other firearms.

So, let’s begin:


MP7 A1 and MP7 A2 in 4.6 MM X 30. Pictures from the HK catalog.

MP7 from EnforceTac 2017, my picture.


MP5, MP5 SD and MP5 K.

This Classic doesn’t need much if an introduction. (MP5 MLI pictured, from EnforceTac)

The Unicorn, with all modes of fire.



G36 A11, G36KA4, G36 KV3 and G36C.

HK416 A5 11″, HK416 A5 14.5″, HK416 A5 16.5″ and HK416 A5 20″.

Below: HK416. You can note the”G38″ printed on the upper rifle. My picture from EnforceTac.

Detailed picture of the HK416.

G38 below. TFB source: http://www.thefirearmblog.com/blog/2014/09/01/hk416a5-now-g38/.

HK233. Like a G36 Version 2, with a new name but don’t tell anyone. 5,56×45 mm NATO.

HK237. Based on the G36/HK233 but in .300 Blackout / Whisper. HK337. Based on the HK416A5, but in .300 Blackout / Whisper.

HK433. HKs new compact and modular assault rifle generation in 5,56×45 mm NATO.

HK437. A HK433 but chambered in .300 Blackout / Whisper. There is no picture yet.

HK417 A2 13″, HK417 A2 16.5″ and HK417 A2 20″

Below: HK417A2 13″ top and 16.” middle. G28 Patrol with

G28E printed on the bottom rifle. My picture from EnforceTac.



HK123 and HK123K (MG4)  in 5,56×45 NATO. Light Machine Gun.


Features: Safety catch may be applied in all bolt positions, Withstands barrel obstruction test to NATO-AC225/D14, tandards (soft core, dual core and steel core ammunition DM41, DM11, DM31, DM21), Gun mount interface, Full day and night combat capability, Sight rail as per NATO-STANAG 4694 to mount optical/optronic sights. Folding and telescopic buttstock options. Deployment-specific barrel lengths as quick-release barrel with carrying and barrel changing handle. Simple conversion to standard, infantry and vehicle mounted weapon. Almost similiar operation to HK 121.

HK123K (Short)


HK 121 (MG5 A2) in 7,62×51 NATO.

The HK121 in action.

Features: Safety catch may be applied in all bolt positions, Withstands barrel obstruction test to NATO-AC225/D14 standards (soft core and steel core ammunition DM111A1, DM151, DM21A2). MG3 gun mount interface. Full day and night combat capability, Sight rail as per NATO-STANAG 4694 to mount optical/optronic sights. Fixed, folding and telescopic buttstock options. Deployment-specific barrel lengths as quick-release barrel with carrying and barrel changing handle. Easy to convert to standard, infantry or vehicle mounted weapon without the need for tools (< 1 min). Three settings for the rate of fire. Maintenance-free bolt group buffer to stabilise the rate of fire and absorb the recoil. Belt feed with loadedstate indicator

Below: Some of my pictures from EnforceTac 2017 of the HK121, Universal Machine Gun.

Below: The letters “HK121” clearly visible on the cast iron receiver. It comes with a minimum service life of 50,000 rounds. Note the aluminum top with Picatinny rail. Don’t like the color matching? That’s what different surface finishing does to various materials.

EDIT – Reference to the “cast-iron receiver” from the HK catalog.

The gas port on the HK121 can be adjusted without the need for tools, and gives approximately 640, 720 or 800 rounds/min.



MSG90 A2 in 7.62 mm x 51 NATO.

HK241 in 7.62 mm x 51 NATO. DMR Rifle.



AG36/AG36 A1, GLM, HK169, HK269

An overview how the AG36, GLM and HK269s can be used on various rifles, including M4s, C7s and C8s.

Firearms using the 3 digit “new nomenclature” system:

As always, there are no rules without exceptions, so let’s begin with those:

The following rifles use another 3 digit system.

MR223, MR 308, MR556, MR762 (They are for the Civilian market).

HK416, HK417 (Assault Rifles).

And these “Classics” remain as well:

MP5, MP7, UMP, USC, G36, MSG90.

We wouldn’t like some of these to be renamed, would we?


Decryption of the new nomenclature (LEAF Firearms):


First Digit:

Not sure what this stands for. So far 1, 2, 3 and 4 have been used but I haven’t been able to figure out a system, if there is one? Some examples below:

1 HK121, HK123, HK169

2 HK233, HK237, HK241, HK269

3 HK337

4 HK433, HK437 (remember 416 and 417 are exceptions).

Second Digit:

1 Unknown or not used.

2 Machine Gun. Full Auto. Belt fed.

3 Assault Rifle. Full Auto.

4 Rifle. Semi-Automatic.

5 Unknown or not used

6 40 mm System

Third Digit: (Caliber)

1   7,62×51 NATO

2   Unknown or not used

3  5,56×45 NATO

4  Unknown or not used

5  Unknown or not used

6  Unknown or not used

7 .300 Blackout/Whisper

8  Unknown or not used

9 40 mm


Note: As the HK433 should arrive in 7,62×39 mm (Kalashnikov), one of those unknowns will sooner or later revel itself.

Funny enough, it is mentioned in the Heckler & Koch Press Release that the HK433 in 7,62 mm x 39 Kalashnikov would be called HK123. However that name is already taken, but only after that Press Release. And it’s the machine gun previously called MG4. Honestly, I think the names MG4, MG5 etc.are so much better than the 3 digit system and I’m not sure I’ll ever get used to it.

(It’s a bit when BMW decided to change the name of the BMW M3 to BMW M4. Because the M3 has 4 doors and the M4 has 2, well let’s say I’m still struggling getting it right.)


HK433 Press Release HK433 01.03.2017

From the HK Homepage: HK123. That’s a machine gun in 5,56, not a HK433 variant.


In the HK 2017 catalog there is also an interesting chart showing the weight of various rounds and the potential combat load (rounds).



If you find any errors or know what the missing digits stand for, please write below.

Eric B

Ex-Arctic Ranger. Competitive practical shooter and hunter with an European focus. Always ready to increase my collection of modern semi-automatic firearms, optics and sound suppressors. Owning the night would be nice too.


  • Archer

    There is something for everyone.

    If you have the money.

  • Anonymoose

    The HK11 and HK13 were the automatic rifles. They were basically HK21s and HK23s that had a magazine adapter to use G3 or HK33 mags, or the famous 50-round drums that were the ancestors of the X-products drums.

    • SP mclaughlin

      I still want to see an HK21-or the like on Forgotten Weapons.

    • Eric B

      Thanks! Except this wasn’t a history lection (but enjoyed yours), or trying to write a book, but the modern firearms currently on sale in HK’s catalogue.

      • Anonymoose

        Yeah, I just wanted you to update your table. 🙂

    • SGT Fish

      this comment makes the whole article make sense along with Mike Cramer’s comment below. I remember there was a group of guys thinking about trying to make some HK25s because all those full auto HK sears could be used with them. Adding even more versatility to the transferable sears

  • PK

    “HK121 … cast iron receiver”


    • mosinman

      i also noticed that..

    • Frank

      So I can sear a steak on it between firefights?

      • Dr. Longfellow Buchenrad

        For that kind of money Id better be able to do it during a firefight.

    • Eric B

      That is what the catalog says, see new picture in the post. Don’t kill the messenger.

      • Dougscamo

        It really does look as it is constructed of cast iron….interesting….

    • FarmerB

      Probably a mistranslation of forged steel.

      • PK

        I did some digging, and it really is cast, surprisingly! It’s steel, not iron, but it’s actually a cast receiver. Apparently it works very well, better than the usual HK choice of sheet steel, and is cheaper, and is substantially stronger/stiffer. It’s an unusual choice, but quite appropriate in this instance.

    • Joby

      Does it have to be seasoned with CLP?

  • Brett baker

    HK is as bad as Colt in it’s numbering system.

    • SP mclaughlin

      Honestly Colt’s is waaaaay more confusing

  • Walter E. Kurtz

    I got a headache reading this. The horror….the horror…

  • Friend

    I like the beard on the guy in the 121 pic.

  • DropGun25

    So happy to see some gun pron after being inundated with Sig crap…

  • Mr. Katt

    HK where the more complicated the numbering, the most useless it becomes.

  • doyle hill

    That G36 is But-Ugly & fragile looking and the stock on the 433 looks mis-proportioned like the arm on Kuato from the original Total Recall… “Quade, start the engine…”

  • Mike Cramer

    In the 2 digit system (91, 93, etc) the first number denotes barrel length and second caliber. 9 being full length, 5 being short version.

    Second number is calibre,
    1 = 7.62×51
    2 = 7.62×39
    3 = 5.56×45
    4 = 9mm

    1 and 3 match with the calbres above, 2 would work for x39, as would 4 fit in for 9mm. However 7 is listed as .300 blk, while the MP7 is 4.6×30.

    At least this is according to my research.

    • Chris22lr

      x9x is for US civilian imports.
      x4x is for all other civilian markets.
      x3x is for full-size (or shortened K variants) automatic rifles
      x5x is for sub-machine guns (or rather compact carbines since it’s not limited to pistol-caliber SMGs)

      MP7 is Bundeswehr designation and it got nothing to HK naming convention (it would be probably something from x5x range, or not at all since it’s more of a pistol and HK pistols don’t follow HK convention).

  • Uniform223

    Before purchasing H&K products, be sure to consult a financialist…

  • So you basically just felt like posting HKs entire inventory for no reason?

    • Eric B

      There’s always a reason to do that.

  • Dr. Longfellow Buchenrad

    The BMW system isnt quite as complicated as the HK system; though it has been getting worse. Pretty much each pair of numbers (1/2, 3/4, 5/6, 7/8) corresponds to a different size chassis and the odd number is the sedan version and the even number is the coupe version (Coupe being a strong word here with the recent trend of “4 door coupes”).

    Its the second and third digits of the cars name that have become quite distorted. It used to exactly denote the size of the engine in liters (except in a few rare instances) until the 2000s came around and once they started to turbo things in 2007 it all went out the window. Now you can get a 2.0L that is a 20i and a 2.0 that is a 30i and a 3.0 that is a 40i. Its completely incoherent.

    This is a recent frustration of mine trying to make sense of the BMW product line that was unearthed by the BMW comment. Rant over.

    • Dougscamo

      I should be so lucky as to have this problem….

  • D

    Now with the new Georgia facility being built may be we will see all the goodies from hk that we want? Maybe some new option like 10mm usp/vp maybe mp5/10?

  • Chris22lr

    This is not a new nomenclature. It’s good old HK naming convention, as used on guns like HK33, HK21, HK91 etc. The only difference is addition of the third number (in front of the two other digits), which differentiates between separate weapon designs. Check out the article on HKPRO site for better overview of original two-digit system.

    The confusion comes from the fact that most-known HK guns use either German gov. designation (G3, MP5, G36, MG4, MG5, G28 and G38 – which is HK416 adopted by some LE formation) or (in case of HK416) name which points to the origins of that gun (US rifle M16 and carbine M4). Judging from the name of HK337 .300BO gun, “non-commercial” designation for HK416 would be HK333 (and HK331 for HK417).

    The HK123 refering to HK433 is probably an error – HK123 was always a name for the gun which was adopted by Bundeswehr as MG4. 7.62×39 variant of HK433 would be HK432. Trivia: HK also made a short lived HK221 MG which was a FN MAG variant.

    I see only one “hole” in the whole HK system, which is G36 and it’s variants. G36 should have a HK133 designation (since HK33 is a roller-delayed 5.56), with HK233 as a separate family. However HK237 is clearly based on G36 (the way upper rail and handguard are attached are of G36 style, not HK233). So this could mean that either HK237 in it’s current form is only a prototype (and we will see “proper” variant with HK233 design cues later), or that for HK guys the G36 and HK233 (despite their differences) are all part of one gun family (this would make G41 a possible candidate for HK133).

  • Chris22lr

    The “old and functional” system you’re referring to is still a thing. It’s a German Bundeswehr/LE naming convention and it’s not limited to HK guns only: G1 was FN FAL, MP2 was Uzi, MG3 was Rheinmetall’s 7.62x51mm version of MG42, G29 is Haenel’s RS-9.

    It’s like a difference between Colt Model R0920 and M4 carbine.

  • mazkact

    HK 121, “Cast iron receiver ” ? That does not sound right.

  • retfed

    Is H and K going to come out with a wheel, like Smith and Wesson did back in the 90s, so you can figure out all the different number combos?

    • Dougscamo

      Ouija wheel?

  • Zi’ang

    Thanks for the article! I’ve had little to no questions for the 2nd and 3rd digits, but allow me to propose what the 1st digit means:

    1st digit:

    1 HK121, HK123, HK169
    **the 1 digit is used for already developed heavy weapons of .30cal and above which have transited over to the new naming nomenclature

    2 HK233, HK237, HK241, HK269
    **used for new firearms which are improvements of the existing G36 platform, including UBGLs for the family

    3 HK337
    **used for new firearms which are improvements of the existing HK41_ platform

    4 HK433, HK437 (remember 416 and 417 are exceptions).
    **used for new firearms which are based on HK’s new modular assault rifle design

    For this new classification to make sense, we have to completely factor out weapons with legacy names (HK-xx ; Gx ; MPx ; UMPxx ; MGx) to prevent confusion and inconsistencies. It wouldnt make sense to muddy the waters by including legacy weapons with the HK-xx classification because of the lack of correspondence in digit numbers, let alone digit implication.

  • Out of the Blue

    Looks like they’re trying to push the MP7 as a high endurance weapon for urban combat based on the chart showing it with 210 rounds more ammo than a 5.56 combat load. That’s seven more GI magazines worth of ammo. Engagement ranges are shorter there, so, at least to the infamous good idea fairy, it might be a worthy trade-off. An “ammo-overmatch” (ammomatch?) angle, to give it a name.

  • Jonathan Ferguson

    Well that’s as clear as mud. So many virtually identical products with different designations. My brain hurts.