GHK AR15/M4/M16 GBBR Drop In Kit Review (First Impressions)

[L473ncy]

Hey everyone. I'm one of the 10 guys that GHK selected to make a review of their Drop in AR15 GBBR Kit. So far I've only done my initial review and first impressions. I'm waiting on some parts to do a drop in/build up and field test but it will come at a later date when I get my parts. I will also be doing an initial field test and one more at the end of the season (hopefully including a take down test) for long term reliability statements and findings. So without further ado here we go:

NB: If I make references to parts numbers the diagram will be shown in the addendums at the end of this post (or possibly on post #2).

First Impressions

Unboxing:

The box itself:

The box is a plain Jane standard cardboard box. Nothing special here. On it you get the GHK logo and link to their website with “GBB BOX AR” in the corner denoting that it’s the AR15 GBB unit. On the side of the box is a little warning blurb about safety and warnings about not being an idiot (eye pro, don’t wave around in public, keep out of reach of children, etc.). Inside the box you get foam cut outs for the things inside. Whether or not it gets changed when it’s released for full production I don’t know but right now it’s simplistic and does the job without any fancy graphics or anything.




In the box you get:

- GHK AR15 GBB gearbox
- 1x proprietary GHK mag
- Samoon/GHK's special water absorbing gel stuff (to help seal the mag from leaks or something? I've seen the youtube video and am still at a loss as to what it does)
- Instruction Manual



Finish of the gearbox and materials:

Out of the box it appears to be fairly well lubed with what appears to be a fairly thin kind of lubricant. If I were to compare it to something I would compare it to either heavy weight silicone lube or “wet” bicycle chain lube.

There are some moulding marks on the innards most noticeably on the metal innards (I believe them to be made of an Alu/Zinc alloy), other metal bits that are steel (or at least slightly magnetic) appear to be non-structurally loaded; the screws, and piece number 12 (which appears to be a brass bushing/bar thing of some sort).

Part number 1 on the upper portion is made of plastic, however parts 2, 3, 5, 6, and 7 are metal of some sort. I’m not so sure about the structural integrity of the plastic of part number 1 but only time will tell if it lasts (short term field testing to come at a later date and long term testing will be at the end of the season). Since it is plastic it will yield somewhat better than metal will but I’m mainly worried about tensile (indentation) strength here seeing as how there is a hunk of fairly heavy metal hitting the forward portion of the gearbox.


Above: Upper front portion of gearbox that mates up to the gas release of the magazine.


Above: Upper and lower portions of the gearbox separated.

Weight:

Using a kilogram scale accurate to .01 kilos +/- .005 kilos. I've measured the following:

Box Weight: 1.06 Kg
Mag Weight: .48 Kg
AR Gearbox Weight: .39 Kg





Above: Picture of the mag and fill valve area (appears to be a modification of the GHK mag for WA system with a different feed lip):

What does this mean? The mags are pretty hefty. They’re slightly heavier than a real AR mag loaded with 30 rounds of .223 Rem. Which I have reports of being on average about .43 Kg. fully loaded. Now you can be almost be like a real “leet spec ops operator” with an approximately correct weighted loadout. But other than that this brings a more serious level of realism to airsoft and although not ground breaking in any way a small detail that will almost certainly add to the end feeling and perception. However the fact that the gearbox weighs less than the mag is a bit worrying for me and feels to me that they skimped out on manufacturing materials and used plastic instead of metal (albeit a decent medium quality plastic that isn’t high quality like Magpul PTS Pmags but isn’t cheap like the old plastic AR15 STAR mags).

Closer look:

Internals:

As for the gearbox unit itself, it seems fairly simplistic and the parts don’t seem to be too complicated. I’m not an expert with GBB systems but it looks to be comparable to a pistol GBB unit. The weight feels lacking but then again like I’ve said earlier plastic does yield a bit better than metal before structural failure so I would hope that it does well for at least a season before showing signs of structural failure.


Above: Internal trigger/hammer mechanism for hitting gas release valve.

Moulding Seams:

Mould marks are very noticeable out of the box. I hope that this is just because of it being a review/prototype model but it doesn’t seem to affect function it’s more of an aesthetic that would give me more confidence in the tooling and production of the GBB box kits. But only time will tell if the parts are up to snuff and there are no major structural failures.



There are a lot of exterior rounds and some interior fillets on the upper and lower portion of the gearbox however there are some places where the gearbox was chamfered (probably to save dev/tooling costs/time) and even other places where it’s a straight corner. The benefit of the fillets is that it will hopefully help to keep the unit from breaking from the stresses placed on it since it’s a “continuous” line as opposed to a single point where stress is placed on it (or at least a multi chamfer). I would have liked to have seen more fillets on the interior of the unit to help keep it functioning for longer but only time will tell if the current design is up to snuff (PS: I’m sure machinists will hate me forever but FILLET ALL THE THINGS!).

Hop up unit:

I like the inclusion of the drum style hop up. It’s much superior to the older M4 3 gear style hop up IMO and since they have their own proprietary hop up unit for the mag to work it’s a nice thing they did. It appears as if it uses a standard AEG style hop up sleeve.

Watch out for the next part of my review where I will install this into a new body. Complete a shooting test, accuracy test, hot weather/cold weather test, and my wear and tear observations.
Also a video review of the unit will be up in the near future hopefully.

Conclusions for now:

For now I only hope that the gearbox costs less than $160 USD (it’s cool that it comes with a mag and it’s special hop up unit but if it doesn’t come with a mag it’s only realistically worth like ~$120 USD). It looks pretty good if you want to experiment but then again GHK isn’t known for making super high quality GBBR’s and I don’t know about how much aftermarket support from RATech and the like we can expect but hopefully someone comes up with high quality aftermarket stuff for things that seem like they would fail fast after some stress (and also an NPAS kit since the Youtube video of Samoon testing the GHK kit shows something crazy like ~150 m/s on .20g with Green/Propane which converted to FPS is ~490 FPS and I’m assuming a relatively normal ambient temperature here). RATech has an NPAS for the GHK AK so hopefully it’s only a matter of time before one for the GHK AR15 gearbox is developed.

[L473ncy]

Partial instruction manual and parts diagram:





Also reserved for future use.