AK Essentials Series–Rifle Dynamics AK to M-4 Stock Adapter

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Jim Fuller’s AK to M4 adapter works great and looks clean. He offers both a Gen 1 and Gen 2 option.

As I’ve mentioned in other columns, the AK universe is like a cottage industry run by men reminiscent of an earlier era.

Working out of garages or barns, they are at once, part entrepreneur, inventor, and engineer. Driven by passion rather than the buck, they live, eat and dream AK.


One of the better known members of this club is Jim Fuller, founder of Rifle Dynamics. Jim builds custom AKs (see his most recent interview from AKOU founder Rob Ski)  and designs specialty parts out of his shop in Las Vegas, Nevada.

Jim strikes me as a very practical guy.

One of his best known creations is an adapter that allows you to easily bolt on an AR stock assembly to the back of an AK receiver. We decided to add the RD adapter to a new Saiga which came stock with a polymer, commercial size tube. We wanted to add a milspec stock to the Saiga and the RD system was clearly the way to go.

This system will work with most variants but will not fit a rifle with a milled receiver, a Chinese rifle (Norinco MAK 90, NHM-91, Polytech, B West) nor the PSL, Zephyr or Yugo.

Why go with an RD adapter?

The RD adapter has been almost universally appreciated by just about anyone who needs to convert an AK.

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Installation is straight forward. It’s pretty much a matter of cinching down four bolts and adding a bit of Loctite.


First off, the AR style collapsible, fixed stock offers an almost infinite latitude for “operators” of every physical description. With one click a 6’4” shooter will be able to use the same rifle as someone 5’4”.

Second, and no less important, is the issue of utilizing optics on an AK.

This original AK was designed for use exclusively with iron sights. Adding an optic to an AK was secondary and hence was never engineered to have the proper ergonomics to support “glass”.

Even with a siderail mount, or adding an optic-mounted to a rail atop the receiver doesn’t always work that effectively. The optic almost always sits too high and/or the stock simply sits too low to afford a comfortable cheek weld.

The operator has to compensate for this by moving up his cheek vertically up the stock in order to see through the optic. This is both uncomfortable and impractical. The Fuller system rectifies this issue by changing the geometry of the stock so that it sits higher, thus giving your cheek weld a vertical boost.

The upshot is that you can more easily get a proper sight picture both with the iron sights and if you so choose, optics.

Gen 1 and Gen 2

We installed the original, “Gen 1” version of the product. There’s a slight difference between it and the Gen 2.

The Gen 2 system has the stock at a slightly lower angle. He did this because some users suggested that the angle of the Gen 1 was so high, they couldn’t use the iron sights efficiently. (As a Gen 1 user I haven’t found this to be an issue.)

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The real trick is making sure that you placed the adapter squarely aligned with the back of the receiver.

In addition, Jim has added a couple of polymer shims to Gen 2 for the screws that bolt the adapter onto the tang. He did this to help prevent stripping the screws by over tightening.  Evidently too many people got overzealous with the Gen 1 system when it came to cinching down the screws on the tang.

Jim reminds users not to torque the bolts down too hard. Common sense dictates that tightening them moderately with Loctite will work quite well.  

Installing the RD system

Adding the adapter essentially means adding four bolts. However there is a technique to getting it to fit perfectly. (Jim demonstrates this in his video which I recommend looking prior to installation).

When I say perfectly I mean getting the adapter squared with the back of the receiver. As mentioned above, you’ll need to this with the assistance of some Loctite so it will have to be done in an efficient manner. It’s not as easy as it looks so take the time to watch the video


The end result is both aesthetically pleasing and very robust. What I also liked was that there no need to cut off the stock tang. On the contrary, RD has designed the adapter so it utilizes the tang to make the system extremely strong. Additionally, any sling adapter that fits on the AR buffer tube should work with this set up.

Shooting my Saiga, after mounting the adapter, felt ergonomically “correct” and solid. It was comfortable to use and a real improvement over the polymer buffer tube arrangement. I was able to use both the iron sights and a red dot with no hassle.

I think you’ll be happy with this too.

Photos courtesy of On Target staff.

Questions?  Comments?  Contact us at ontargethawaii@gmail.com

Rob Kay writes about firearms for Hawaii Reporter and is the author of How to Buy an AK-47.

Read more of Rob’s articles on OnTargetHawaii.com