HS Produkt VHS-2K Airsoft Replica Build [Part 1: Barrel Assembly / Mock Gas System]

 

 

This is the barrel assembly and mock gas system for the VHS-2K. Everything pictured in silver is going to be a metal component - most parts will be aluminum for ease of machining on my very basic lathe setup, but the springs and spring shafts will be steel.

Each of the featured parts has a specific name. Familiarizing you with all of them would be quite a pain in this format, so for the sake of brevity, here's just the names of the relevant parts, front to back:

1. Gas block adjustment knob (PLA+)
   
2. Gas block (PLA+)
   
3. Accumulator (Aluminum: 12mmOD, 10mmID)
   
4. Forward interface (PLA+)
   
5. Piston (Aluminum - 10mmOD, 3mmID)
   
6. Charging handle interface (PLA+)
   
7. Charging handle spring guide (x2) (HSS)
   
8. Charging handle spring (x2) (Steel)
   
9. Chamber (PLA+)
   
10. Chamber extension (PLA+)
    

The majority of these parts exist so the charging handle can be pulled and not break something. I also wanted the charging handle to feel substantial when you pull it and wanted to try to use this assembly to counterbalance the relatively hefty FAMAS gearbox, hence making a lot of it out of aluminum and steel rather than just plastic.

In order to successfully mount the gas block in such a way where it would key to the outer barrel, I needed to print a jig to guide a drill bit so I could easily cut out just a small amount of material perfectly aligned with the top of the barrel key in the rear. Luckily, from the host replica's gas block, there were two divots in the bottom of the barrel I could use as keys.

The damage to the jig was planned - it was made a very tight fit so it wouldn't rotate easily while drilling, so removing it damaged it a bit. The drill bit unfortunately walked very slightly on the front cut, but the visible offset is mostly just surface-level and doesn't affect anything.

With that done, it's finally time to start printing and machining parts.

One, two... skip a few...

Machining the "piston" SUCKED because the only tooling I have for my crappy little lathe is a single cutoff tool and a dull HSS cutting tool. Took me around 2 hours to get it done as a result, taking away a hair's width of aluminum at a time... but it's done now. Later I will probably buy some cheap tooling to do a finishing pass and then give it a mirror finish with some sanding pads and buffing compound. Totally fine for now, though.

I initially designed some clips to go on the front of the spring guide rods to retain the charging handle interface and the springs, but realized as I was assembling everything that they weren't necessary. The only retaining clip I wound up keeping was on the rear of the charging handle interface (dead center in the second picture) - and that's just to allow the charging handle to actually pull the piston rod back.

I used aluminum pin stock to make the indexing/fixing pins for each of the parts that needed them - here's the gas block for example. I cut them with a band saw and added chamfers by chucking them in my drill press and raking them with a file. Didn't need to be exact, just needed to easily slip into the holes and not get caught up on anything.

 

 

And that's all there is for the barrel assembly and mock gas system. All things considered, this went together really easily, and I'm quite happy with the end result. In the next part, we'll get started on the upper receiver and fitting the barrel assembly into it.

 

-Craig, ETW