TFB Review: How To Build A Pistol SCAR17Shorty With Imperial Arms Co’s CYPHER X

    side profle of SCAR17Shorty


    If you recall at the beginning of the year we posted about the Imperial Arms Co CYPHER receiver. It is a virgin receiver that is SCAR compatible. Imperial Arms Co sent me a CYPHER X so I built it into a pistol that I call the SCAR17Shorty.

    How To Build A Pistol SCAR17Shorty

    Firstly I will eliminate any disillusions you may have. At the moment you cannot make a pistol SCAR without a donor gun. If you think of it like the Netflix show, Altered Carbon, we are re-sleeving the SCAR into a virgin receiver. While there are some places to buy most of the parts you need like Midwest Gun Works (MGW) it is hard to find all the parts you need. Especially the bolt carrier and bolt. The other problem is that it is not cheap. FN sells a 13″ barrel assembly for $1499.99 but it is discontinued. MGW has the barrel assembly for only $1,149. Add the $750 for the bolt carrier assembly, if it was in stock, now you have spent $1,899 and you still don’t have the lower receiver, all the small parts or the actual serialized receiver. This is why I decided to just harvest all the parts from my FNH SCAR17S and transplant them into the virgin CYPHER X SCAR receiver. For the barrel, I removed my 16″ barrel and sent to Taylor Pickerell of GNI to chop it down to 13″. I did not want to go to 10″ as I imagine the muzzle blast would be atrocious and I am not interested in making a flame thrower.

    Taylor is well known for chopping a lot of barrels down and rethreading them concentrically. He always runs a muzzle device alignment rod to show it is concentric.

    The barrel chop cost me $125.

    Old Vs. New

    The day I picked up the CYPHER X, I bought a Glock 44 as well.

    Here is my original FN Herstal SCAR17S receiver compared to the Imperial Arms Co CYPHER X receiver. There are some aesthetic differences but otherwise, they are very similar. The CYPHER X receiver came anodized black. I did not want a black SCAR pistol so my friends at CROM USA helped me out and Cerakoted the CYPHER X along with some of their parts. They used Elite Cerakote colors and made a woodland style pattern. It is different and unique. Definitely better than plain FDE or Black.

    There are some milled out pockets along the CYPHER X but it isn’t really for weight lightening. More for aesthetics.

    There is one big difference between the CYPHER X and the FN Herstal receiver, the CYPHER X has a pin you can see below. According to my friend Buddy M., who built a 20″ 6.5 Creedmoor using his CYPHER X receiver, that pin was required by ATF to prevent the CYPHER X from being converted to full auto. Not sure why they need it but FN Herstal does not for their semi-auto SCAR17S.


    These are all the screws that hold the SCAR17S receiver and parts together.

    So you got your CYPHER X receiver and your SCAR17S. Start taking the SCAR17S apart. Field strip it then start removing all the upper receiver parts. Mine already had the side Picatinny rails removed so I skipped that part. You need to remove the barrel assembly first and that is just 6 Torx screws. The two Torx screws on either side of the black pieces are captured and ratcheted so don’t waste your time trying to unscrew them out all the way.

    Sometimes while removing these black pieces the clips and Torx screws fall out.

    Here is how they go back in. Install the screws in first. They go up from underneath the plastic part then install the metal clips.

    The barrel assembly slides halfway forward then you pull it down out of the upper receiver. Remove the front plate, rear plate and the receiver rail. You can see the receiver rail in my disassembled SCAR17Shorty a few pics up or in the photo with all the screws, it is behind all those screws. However, I cannot seem to find that part on Midwest Gun Works parts finder.


    But I was able to find it after looking on the 8th page of parts. Click here to see the part. You can see where it goes in the CYPHER X below.

    So now just reinstall all those parts back into CYPHER X receiver. The T-nut for the barrel screws sits in this small channel. Make sure it is aligned properly before you start screwing down the black part. Don’t overtighten otherwise you will crush the plastic.

    Torque the receiver screws to 32 in-lbs and the barrel screws to 62 in-lbs. Then reinstall the bolt carrier group, charging handle, recoil spring and guide rod.

    What About The Back Side?

    Since I am building my CYPHER X SCAR17Shorty as a pistol I wanted to put a brace on the back. The factory SCAR17S uses the stock to hold the guide rod and lower receiver in place. So unless I SBR this thing I am going to have a brace on it. I went with a JMAC Customs rail adapter. This allows me the most flexibility for adding a brace.

    With a Picatinny rail adapter, I can use the new metal FSB1913 brace. The cheek rest is made of metal compared to their first release version which was all polymer. I have used the polymer version on my MP5K and it flexes too much for my liking, so a short barreled .308 would be worse.

    Another option is to use an AR buffer tube and SBA4 brace.

    There is a third option and that is to get a tailhook adapter from Dan Haga Designs and put a GHW Tailhook on an ACR stock.

    Photo by Dan Haga Designs

    Photo by Dan Haga Designs

    I have the Kinetic Development Group ACR stock for my SCAR17S and the last time I shot it, with the machine gun optic and when I tested the American Marksman ammo, it was unpleasant. So I decided not to go that route.

    I decided to ditch the factory PWS muzzle brake and went with a SureFire flash hider. It is still very loud. Below is a comparison to my friend Kythe’s SCAR17S rifle next to my SCAR17Shorty pistol.

    Shooting The SCAR17Shorty

    Just like the full length, it is loud even with a flash hider. It recoils a bit more but that could be because I am not running a muzzle brake anymore.


    One issue I had was with the FSB1913 folding brace. The recoil was rather significant when rapid firing and the brace started to unlock and fold on me. So I would have to twerk the back end of the receiver to manipulate the brace back into position.

    Accuracy is the same as before but the range is a bit reduced. Here I fired out to 600 yards to get an idea where it was shooting.

    Then I went to 800 yards.


    Final Thoughts

    While there is no cheap way to build your own SCAR17S, the Imperial Arms Co CYPHER (16S) and CYPHER X (17S) receivers do offer options for some shooters. For example, if you live in a state with restrictive tyrannical assault weapon laws, like Connecticut. The FN SCAR is banned by name there. With the CYPHER X or CYPHER, you could have a SCAR rifle converted to a CYPHER receiver and build it as an OTHER FIREARM. You could even go OTHER FIREARM route like in California. Franklin Armory set the path for OTHER FIREARM in California with their Title 1 firearm. While different than the Connecticut Other Firearm, it is an option to exercise freedom behind enemy lines. And no, moving to another state is not an option and all the voting hasn’t helped yet. Hopefully, all the people panicking to buy guns in CA during the “shelter in place” emergency protocols for battling COVID-19 will awaken people who never realized what a mess it is to get a firearm in California and will vote better next time to preserve and possibly revive their full 2A rights like the rest of the country. One can only hope.

    If you want to build a SCAR17Shorty or build one to comply with some restrictive state then check out Imperial Arms Co.

    Nicholas C

    Steadicam Gun Operator
    Night Vision & Thermal Aficionado
    Flashlight/Laser Enthusiast
    USPSA competitor

    Any questions please email him at [email protected]