TFB Review: DIY KelTec RSB SU16 Bullpup – The Fugliest Bullpup

    Last February my FFL acquired a large estate sale of firearms. Most of them were mundane Girsans, Bersas, and PSA lowers. There are other guns but the Keltec SU16 box piqued my interest. This is where I discovered the fugliest bullpup. When we opened the box, this abomination was lurking inside. We were so confused by what we saw. I looked at it more closely and decided I should adopt this SU16 bullpup and share it with the world.

    KelTec @ TFB:

    The Fugliest Bullpup Is A DIY SU16 Bullpup

    When you think of a KelTec bullpup rifle you think of the RFB or RDB. Well, this could be considered a KelTec RSB (Rifle Side-eject Bullpup). But I prefer to refer to it as the SU16 Bullpup or the “fugliest bullpup”. I challenge you to find an uglier bullpup. This is not a factory option. This is a custom gun some mystery person concocted.

    SU16 bullpup

    Someone had surgically neutered the stock and got crafty. It appears this SU16 Bullpup may have been an SU16C before its reassignment surgery.

    Photo by KelTec

    It appears he cut the stock off and epoxied it onto the top of the receiver as well as added a healthy amount of epoxy to build up a cheek rest. Below is a quick edit I did in photoshop. You can see it come together. To be honest, the photoshop below does not look half bad. The epoxy cheek rest is what makes it look bad. What is smart about this design is that the length of the SU16 has not significantly changed from its folded form. Maybe a few millimeters were added with the relocation of the buttpad/stock. But it still has an OAL over 26″ and a 16″ barrel.

    A forward trigger, trigger guard and pistol grip were added to the barrel. Yes, the factory trigger still works, you can pull it to fire the SU16 bullpup as well.

    The downside to this design is that the linked trigger wire gets in the way of the factory trigger group from folding thus not allowing you to field strip the SU16 Bullpup. I tried to pull the trigger linkage wire out but it did not want to budge and I was afraid I would break something.

    This gunsmith also chopped the factory front sight off to weld a metal block and bolted a Picatinny rail on top of it. The bipod handguard has been cut to accommodate the new trigger group, trigger guard and pistol grip block.

    We Have Valmet At Home

    Photo by Guns Wiki

    If you squint, the SU16 Bullpup somewhat resembles the Valmet. Both are chambered in 5.56. They have a fixed charging handle on the right side of the bolt. Both are piston driven and of course, they are both bullpups. They both have linked triggers however the Valmet uses a bar to push the factory trigger, while the SU16 bullpup uses a thin wire to pull the factory trigger. See the wire below. It sits above the hinge point of the forward trigger so when you pull the trigger back, the wire is pulled forward. It is easier to pull a wire than to push a wire. This allows you to use a thin wire whereas the Valmet uses a thick steel bar to prevent bending when you actuate the Valmet trigger.

    I am not sure if the gunsmith custom fabricated this trigger block or used something from another gun. Considering how blocky it is and the custom nature of it, I suspect it is custom. In order to install the trigger block, he had to remove the factory gas block, slide this trigger block over the barrel and reinstall the gas block. Then he bolted the trigger block down to lock it to the barrel. Then attached the forward trigger, trigger guard and bolted the pistol grip. I upgraded it to a Magpul MOE-K grip. Even though the length of pull is ridiculous I prefer a more vertical grip.

     

    The trigger wire travels rearward under the handguard’s left side bipod leg.

    The trigger wire sits under a horizontal ridge and over the screw boss below. This helps to protect the wire from snagging on anything. Then there is a hole cut through the side of the receiver and a hole drilled into the trigger with the wire going through that hole.

    Modernizing The SU16 Bullpup

    Since the creator of this monstrosity welded a Picatinny block to the sight tower, I can attach any optics and accessories I want. I am just limited to a mere four inches of rail space.

    I’m using a Steiner ITAL with MPS directly mounted to the ITAL body. I changed out the QD mount for a Unity Tactical Fusion Hub and mounted a Weltool weapon light to the side.

    The bipod handguard still functions.

    Phased Plasma Rifle At Home

    Why am I comparing the SU16 Bullpup to a Valmet M82? Because of this photo of Michael Biehn when he portrayed Kyle Reese in the 1984 Terminator movie.

    The optic on the prop rifle is some pseudo futuristic CRT scope made for the movie. Looks like an ordinary scope with a box fabricated around it. However, there is an optic that looks surprisingly similar. The FLIR HISS. My friend Vic brought out his HISS and I mounted it onto the fugly bullpup.

    We have a phased plasma rifle at home. Photo by Vic.

    Bullpup Vs Folding Rifle

    My friend Jerry has a factory SU16B with compact forend so we took it out to compare it to the SU16 Bullpup.

    The SU16 bullpup weighs 5 lbs 14 oz (without the optics/laser/light HUD) whereas Jerry’s lightweight SU16 is just over a pound lighter at 4 lbs 12 oz. Lengthwise, the SU16B is 35.9 inches long and I measure the SU16 Bullpup, with muzzle brake, at just 27.25 inches. So a good 8.65 inches shorter.

    Shooting The SU16 Bullpup

    Since the SU16 bullpup sits lower in my shoulder pocket, it feels like a straighter push rearward. Perhaps it is the muzzle brake as well. But watch the video below. Since my face is sitting on top of the receiver, instead of below and behind it, the bore is in a lower position in my shoulder. I do notice I have to really shove my cheek down and forward to get a decent sight picture through the Steiner MPS. I even have it mounted on top of the ITAL laser thinking that would give me plenty of offset for a good sight picture. Not as well as I had planned but it works.

    I can feel the action of the SU16 next to my head as it cycles. Not the case with the SU16B rifle. After reading up on suppressing the SU16 is not supported by KelTec, I decided not to risk breaking anything on the SU16 Bullpup by suppressing it. The only real issue is the manual of arms to operate the SU16 Bullpup. The safety and magazine release are not in a good position. I find myself manipulating the safety, magazine release and charging handle with my left hand. An ambidextrous magazine release would be a great improvement.

    Final Thoughts On The SU16 Bullpup

    I only shot a few magazines through the bullpup and it ran without issues. I did notice the trigger guard felt a bit hot. I tried to utilize the bipod handguard and that was a mistake. If you look at the photo below, you can see the barrel is directly above my hand. I touched the barrel ever so briefly and felt the heat. I did not get burned but I could easily see getting burned if I shot this a lot more. This makes the handguard bipod useless other than acting as a heat shield for your hand when it is closed.

    The trigger guard is acting like a heat sink since it is attached to the trigger block which is bolted to the barrel. All the heat from the barrel will soak into that block and down into the trigger guard. Possibly even the trigger since it too is made of metal.

    I was tempted to cut the plastic factory trigger bow and trigger guard off since they do nothing and are redundant but I decided to leave it as-is for now. The SU16 Bullpup will function without those parts but it will be a permanent modification. There will be no going back unless I buy a new trigger guard and trigger from KelTec.

    I did discover that some SU16 owners have been upgrading their rifles with Magpul Zhukov handguards. Sadly, the aluminum bed will not fit the SU16 Bullpup due to the trigger block, I tried.

    Photo by NCLivingBrit

    For how fugly this bullpup is, it functions and works as expected. If the repurposed stock/cheek rest were better executed, this would not be the worst DIY bullpup out there. However, I am glad I own this and hope you enjoyed reading about this fugly bullpup.

    Nicholas C

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

    Any questions please email him at [email protected]


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