Easiest SBR conversion ever

We have a few short barrel rifles in the house, and almost all of them have required modifications to put them into SBR status.

For example, I had to drill two holes in the rear of my Mini Draco receiver, which required the use of a drill press, a lot of cutting oil, a carbide drill bit, and a lot of swearing. I also screwed it up a little bit.

The KPOS Glock SBR enclosure made by Fab Defense should have been easy, but the setup is so finicky — you have to rotate the retaining tab a certain way or there is either too much or too little torque on the polymer Glock frame. The KPOS charging handle may have to be adjusted. If your Glock is out of alignment it makes it very difficult to pull the slide all the way back.

My PPS-43C has been a nightmare, and despite having the NFA stamp from the ATF I still haven’t activated the folding stock.

The She-Shepherd’s AR15 SBR was easy, but required an armorer’s wrench. The use of a specialized tool, no matter how simple, is more of a hassle than one that doesn’t need a tool.

My AMD-65 AK47 was pretty straightforward — just use a jeweler’s saw to cut the weld on the 4” muzzle brake. However, that requires a saw, effort, and time. Not a major pain in the ass, but not a super fast conversion.

I recently received my stamp for my Serbian Zastava M92-PV pistol. I could have either drilled the trunnion for another folding stock adapter like my Mini Draco, or drilled for an underfolder stock, but I wanted to avoid any machining.

I cheated and bought a folding stock mechanism from US Machinegun, and it was the easiest conversion ever. So far. 😉

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Design and construction

The US Machinegun setup is made of a folding stock adapter and a solid billet aluminum stock. There are different stock shapes; I purchased the one inspired by the Galil design.

The stock adapter folds to the left, which is my preference. Folding to the left means you can easily run the charging handle, but also means you can’t use a receiver-mounted rail (if you have one).

The folding stock adapter can be opened by pulling on the stock. You push down on the hinge to close it. After evaluating other folding mechanisms I am not particularly fond of this one.

The most interesting part of the stock setup — and why it’s so easy to install — is that there is also a piece that fits between the grip and the receiver. This mounting adapter is made out of solid metal and cradles the receiver.

Installation

If you’ve ever changed the grip on an AK pattern rifle then you can install this stock.

  • Unscrew and remove the existing grip. If you are using a stock AK grip you may not need a different bolt.
  • If your AK does not have a captive grip nut on the inside of the receiver you will need to remove the dust cover and recoil spring. Remove the grip nut.
  • Put the US Machinegun stock onto the bottom of your AK receiver.
  • Put the grip back on. I replaced the stock grip with a MagPul MOE AK grip, and I had to slide the grip on. I also used the bolt included with the MagPul grip. US Machinegun ships the stock assembly with a bolt, and you have the option to ask for a different bolt if you intend to use an aftermarket grip. The MagPul one was slightly longer, and I figured that more purchase would be better than less.
  • Replace the recoil spring and dust cover if needed.
  • All done.

I know you’re going to ask — and I have the same question — is this setup stable? On one hand, it seem janky to hold a stock onto a rifle by just one bolt. On the other hand, I’ve never had a grip shear off in my hand during firing.

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I have a huge list of things to test during training this season, and I hope to squeeze in enough trigger time with the US Machinegun stock to determine how durable it is.

In the meantime, the unit is well built and SUPER easy to install.

It’s been the easiest SBR conversion ever — so far.

About the Author:

Short Barrel Shepherd Short Barrel Shepherd is a regular guy and works to make Web sites and mobile apps easier for people to use. He spends his free time attending fight-focused firearm, knife, and combatives training, motorcycling, writing, and playing games. His daily carry is a Glock 19 pistol and an AR15 .300 Blackout pistol in a backpack.
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4 Comments on "Easiest SBR conversion ever"

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  1. David says:

    As you said… it’s real hard to feel confident about a stock attachment mechanism like that. I’m not a huge fan of the simple-drill-and-tap school of putting a stock on AK pistols, either, for that matter. I feel like you’ve got to drill and tap plus mount an internal reinforcement plate to really get it on solidly.

    If I ever move out of this state, I’d rather go the CNC Warrior route for my next AK SBR. They’ve got M85 and M92s in non-NFA rifle format, and all you’ve got to do is drill out the back part of the pin to remove the fake can. It’d be cool if they could get in the M85NPs…

  2. B R KURTZ B R KURTZ says:

    Living in the Occupied Zone, we don’t have access to any AK pistols and our newest loss of freedom makes future SBRs even more limited. Nonetheless, the SUCHKA you’ve built looks amazing. As too the issue of the durability and strength of the stock being held solely by the grip screw, well You would know best.

    The pictures look like there’s a bit of a cup that fits around the receiver, if so Im guessing that gives the stock more “bite” than just friction held in place with the grip screw; but Id also suggest even the original AKSU’s weren’t really intended for much “Butt Stroking”.

    In either case a round of M43 ball beats a “butt stroke” any day, and you don’t need the stock for that!

    Best

  3. Adrian says:

    Of the two which did you find easier to add a stock to, the Pap M92 or Mini Draco? Why was it easier? Why was it more difficult? Thanks keep sharing the great info.

    • Short Barrel Shepherd Short Barrel Shepherd says:

      PAP M92 by far. I drilled and tapped the rear trunnion on the Mini Draco, which also required the use of a drill press. I did a shitty job, to boot. If I had to do it over again I would either take the M-D to a gunsmith or use the US Machinegun adapter.

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