At Enforce Tac this spring Heckler & Koch Germany displayed the HK237 and HK337 officially for the first time, but there were no details to be had. Now we’re teased with some more technical details.

Heckler & Koch may not like me, or you, but I am in love with the looks of the HK337. But I do like short AR15s / M4s overall, and a LWRC IC-PDW is a beautiful thing except it’s not a 300 BLK.

The HK337 could be my favorite looking HK thing since the MP7. Mount a sound suppressor and the Honey Badger PDW may not be dead after all? Typically H&K runs B&T sound suppressors on their rifles.

228 millimeters is 8.98 inches. That’s the length of the HK237 and 337 barrels. A bit longer than the original Honey Badger, and a bit less refined in some sense, but this one is making it into at least some sort of official volume production.

While the HK337 uses the HK416A5 as a base, the HK237 comes out of the G36 and the HK233 models TFB recently wrote about.

Instead of 5,56 x 45 mm, these models run in .300 Blackout / Whisper. And as you can see in the picture below, which was taken in Heckler & Koch’s booth besides the rifles, that makes quite a difference in terms of bullet weight.

You can notice that the angle of the pistol grip on the HK337 is much steeper than on other models, similar to the Magpul MOE K2 grip. The K2+ grip is my personal favorite, and works well on PDWs, but I don’t mind them on long range rifles either.

Or as Magpul themselves describe the K2 grip: “The steeper vertical grip angle is optimized for use on PDW (Personal Defense Weapon) configurations and improves comfort and control on short LOP rifles that bring the primary hand in closer to the shooter’s body.”

I think HK calls their grip the V2.

For the HK337 pictured, I think there’s room for improvement for someone looking to making their rifle even more compact. If there’s an HK416C PDW stock around, please put that on the 337 and send us a picture.

The signature JS helped translating the German in the magazine ES&T 6/2017 into English:

The *37-series are 300Whisper/300BLK variants as possible ancestors to the MP5 in situations where there’s a need for a higher ballistic power than a mp. The 237 is based on the G36, the 337 on the 416 and the 437 on the brand new 433. The system is manly based on their 5,56 brothers so you don’t need to train with the expensive Blackout ammunition, but still train one to one. The only problem till now is how to mark the parts especially mag and chamber as BLK or NATO so there won’t be confusion in rapid situations

 

Below: This is a close as I got to the HK237 in the spring of 2017 at EnforceTac Germany.

It’s frustrating when companies put their objects of interest behind a reflective glass, onto which they beam massive amounts of light. It makes it virtually impossible to get a good photo, but with some editing in Photoshop some of the plastic and metal from HK Germany came out OK.

Note the metal vs. polymer parts. Unlike the HK433 which seems to have had several revisions of the upper and lower, the HK237 seems fixed in design. Reference to earlier TFB article on the subject HERE.

 

Over to the “337”:

 

The “D” in Modes of Fire stands for “Dauerfeur.”  That’s what you and I call Fully Automatic Fire.

Below: The HK337 in Europäische Sicherheit & Technik 6/2017.

 

EnforceTac show guns had metal magazines. Press picture has polymer.

The RUAG portfolio of ammunition for these rifles. Notice the .300 Whisper SWISS P Final edition 200 gr.

Looks mean, like a Black Hole that wants to swallow you.

For the HK437 there are no pictures or technical data available yet. All we know is that it is going to be a fully-automatic “assault rifle” in .300 Blackout / Whisper.

To remind you, this is what the HK433 in 5,56×45 NATO looks like:

We have to imagine what an HK433 with a 9″ barrel looks like until we get some official pictures, and it’s going to look rather nice I think.

The third digit , the “7” in “437” indicates the caliber, and the “7” means .300 Blackout / Whisper.

“1” means 7,62×51 NATO (ex. HK241) and “3” means 5,56×45 NATO (ex. HK433).

TFB will dig deeper into HK’s new product outline and numbering system soon.

As mentioned before, the HK line of “assault rifles” is getting confusing and this is even before they’ve added more calibers and model names. Most of the data here is HK’s own homepage and offers some help, but all the technical details are far from revealed.

Is HK pushing out model after model in an attempt to increase the company’s value? Or are they releasing new products in a reply to customer’s demands? Regardless of which their factories seem to be pushing full capacity and full shifts.

I think Heckler & Koch are setting up a new system to name their Firearms, to make it easier and more accessible for the upcoming tenders around the world.

Sweden are going to change their AK5 (FN FNC) into something else, Finland are changing or at least upgrading their Valmet RK, Germany too and the list of Nations and Special Forces just goes on and on.

ES&T 6/2017, packed with new products from Heckler & Koch Germany. Source.

HKs overview, from the German Homepage. But this is not the full picture, there are more models around.

Let’s round off the barrel length of the HK237/337 to 9″ (228 mm). To compare the HK416 A5 only comes as low as 11″ (279 mm). The HK417 A2 in 7.62 x 51 mm runs 13″ minimum. Only the G36 C3 in 5,56×45 mm can compete with the same barrel length (228 mm).

Heckler & Koch 237/337, for when you think the MP5 K PDW seems a bit old, lacks sting and should have retired long time ago.

Heckler & Koch 237/337, for when consider the MP7 PDW too small and too much sub of a submachine gun.

It will be interesting to see which countries and which special units that will show an interest in these new HK models.