William Barth posted his custom MP5 that he has been working on for the past two years. His upgraded roller lock free float handguard puts a new spin on roller lock guns and like other gun manufacturers, he has made an adapter to attach an ACR stock onto a roller lock like the MP5.

Back in 2017 pictures went around of an MP5K with an ACR stock mounted on it.

Just like the SIG MPX/MCX stock, the Remington ACR stock has been used on a whole host of other guns than it was originally intended for. Kinetic Development Group put an ACR stock on the SCAR platform and Hera Arms made a trigger housing for the H&K SL8 that utilized the ACR stock.

Below are some more pictures of William’s upgraded roller lock prototype. As you can see it is mounted on an HK53 style gun.

What is even more interesting is William’s upgraded roller lock free float handguard. Here is what William said about it.

There was a discussion in the HKPro forums regarding which rail was better suited for an individual: Knights Armament Company RAS or Surefire Lighted Forearm. I took the opportunity to describe why neither was a good fit for me several years ago and what I did about it.

For me the KAC RAS and Surefire Lighted Forearm were both good options, but I really disliked having to compromise between mounting surfaces or a solid light source. I’m not a huge fan of permanently affixed Pic rails with or without covers and I also disliked compromising on the suppressor installation with the SureFire forearm like you pointed out.

So in the absence of finding exactly what I wanted, I decided to make it myself. I tried to keep it as true to “old school effect” while using “new school tech” to evolve my patent-pending forearm to a new plane of existence. It was designed as a component for a new construction build vice retrofitting an existing firearm, but I’m updating the second iteration to be capable of doing both.

– 6061-T6 Aluminum extruded, machined and hardcoat anodized by an aerospace/defense company
– M-LOK mounting surfaces at the 3, 6, and 9 o’clock positions
– Machined mounting surfaces for add-on rails of any type at the 2, 5, 7, and 11 o’clock positions (My preference is for Parker Mountain Machines rails)
– Retention via 2 cross bolts compressing around the trunion and receiver, so a quick-change setup that is extremely solid. I’ve got a lever-release mechanism on the drawing table for the rifle version.
– Low profile full-length Pic rail the entire length of the firearm. Because of the design adaptability I’m entertaining different rail accessories over the receiver section.
– Front end completely open for any attachment approximately 1.5 inches in diameter, since I wanted to be able to use this on a future SD build as well. The front end is also designed to accept a forearm extension to cover the suppressor.

A lot of thought and planning went into the design and it continues to evolve:

– Ability to be used on “legacy” platforms with rolled receivers. Although all of the firearms pictured are new construction builds, heavy emphasis was placed on ensuring there would be no legal issues. I adapted the forearm around the platform instead of creating a new platform that could not be used with registered sears.

– Ability to quickly install a forward rail extension. The inner diameter allows a user to attach a suppressor so I wanted to be able to cover that with a rail and increase mounting surface for accessories at the same time.

– Ability to be used on all roller-lock platforms. This originally started life as a design for a 21E/23E build but quickly morphed into something much larger.

Works incredibly well on everything I’ve tested it on thus far: G3K, MP5, and a 33. (The MP5 is sporting a registered sear, which helps a lot since the majority of testing has been on auto and with full mag dumps).

I love the ACR stock and have not been disappointed in it at all. The pictured stock adaptor was 3D printed but I’ve got a batch coming back from the aerospace/defense company that are aluminum and oh so pretty. The stock height for me is perfect since it gives me a solid cheek weld with almost every rot dot or scope I run.

I kinda think my forearm on a normal MP5 also gives it a bit of an SD look. And I don’t have to compromise on anything I want to attach to the barrel.

At the moment his handguard design is for newly assembled roller locks. William integrated a cocking tube into his handguard. He will make a new version that will encompass existing cocking tubes but the problem is that they are all so different so he has to make them loose enough to accommodate them all as best as possible.

Here is a test fire on an MP5 with a registered sear.

Given the popularity of his handguard and stock setup for his upgraded roller lock, William is looking to forming a proper company called Revolutionary Roller Locks. You can follow his progress on HK Pro or on Facebook or email him at william@revolutionaryrollerlocks.com