KSG vs. Bullpup Unlimited Mossberg 500 – FIGHT!

I am an unabashed bullpup rifle afficianado. While I shoot an AR/ARAK in competition, I am constant pulled back to bullpups as a solution to many problems, especially home defense. Hank Strange gets his strange on shooting the two side-by-side. 

I have had the liberty to shoot both the KSG and the Bullpup Unlimited kit (in Remington 870 form) and found most of the observations valid and reasonable. That said, I would take the Bullpup Unlimited kit if only for ease of reloading.

What do you think?

*Featured image courtesy of Gunrunnerhell.tumblr.com


Nathan S

One of TFB’s resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

The above post is my opinion and does not reflect the views of any company or organization.


  • claymore

    How many shells does the unlimited one hold?

    • Mr. FN

      Since it’s just a practical chassis for the shotty, whatever the base gun holds. So 4 shells to (at most with a 28″ ribless barrel cut to fit) somewhere around 9 or so.

      • ozzallos .

        Sooooo…. You don’t know.

        • TDog

          He gave a perfectly legit answer. The Bullpup Unlimited is a conversion kit, not a whole gun. The number of rounds the gun you put into it will hold is the number of rounds the BU will hold.

          So the answer is given that most shotguns hold anywhere from 4-6 rounds given an 18.5″ barrel, the answer is 4-6 depending upon the model of the shotgun you use.

      • claymore

        In that case it really is NO CONTEST between the two.

  • Dracon1201

    I think that the philosophy of the KSG is slightly different. You keep both tubes full, then use it as a normal shotgun, and only top it off when you have a moment. cover or otherwise. I’ve tried both. I find both to be just as crappy to load. That being said, the KSG has better controls as it is designed as a bullpup.

  • Bullphrog855

    I just don’t think Bull pups and Shotguns mix well out side of sex appeal. A lot of what it takes to shoot shot guns is the reload, and you simply can’t manipulate a pistol grip shot gun, little lone a bullpup with a convoluted loading port and a mandatory pistol grip like you can with a conventional shot gun.

    But dang it, does the KSG look good.

    • Sianmink

      Reload? No problem.

      • Anonymous

        Unless you’re a lefty, that is.

        • Sianmink

          Sorry, LAV.

      • Phillip Cooper

        Try doing a “select a slug” drill with that thing..

  • TDog

    Having fired both, here’s my take:

    The Bullpup Unlimited is more reliable and has less felt recoil. Out of over twenty rounds fired, I had zero failures to feed or eject. The point of impact seemed be a little higher than what I was expecting from the red dot that had been put on the gun, but as it was not my gun and I had not zeroed in the sight, that was probably due to me holding it like a total schnook. I fired both slugs and 00 buck shot and felt recoil on both was much reduced.

    The KSG I have almost nothing good to say about. The KSG I used – once again, not my gun – failed to feed five out of fifteen rounds loaded. I was initially told to only load five rounds into the right hand tube and those five functioned without flaw.

    Loading ten – five into each – the next time, however, led to some serious failures to feed. Despite the selector switch being in the proper position, the rounds would not feed. I tried selecting for the right tube and then the left tube. Nothing. The gun’s owner told me, “Oh, it doesn’t like it when you switch between tubes.” He then did exactly what I did and selected for the right tube… and couldn’t get the gun to feed.

    “Oh yeah, it really likes to be worked. You have to really rack it.” I’m not a ten-year old girl, so it’s not as if I were tepidly racking the gun with my pinky extended. Apparently racking it requires a steam catapult for assistance to get it to work reliable…

    Felt recoil was reduced over traditionally-laid out shotguns, but there was still a bit of a sting. I attribute this to the gun’s light weight. The sights – MagPul MBUS – were dead on target.

    Overall, both designs are good, but Kel-Tec, as per usual, had a deeply flawed execution. The Bullpup Unlimited stock, however, felt solidly constructed, worked without fail, and allows anyone to turn a spare or used Remington 870 or Mossberg 500 into a bullpup.

    My vote goes to the Bullpup Unlimited.

    • RealitiCzech

      That thing needs to go back to Keltec to be worked over.

      • TDog

        Kel-Tec needs to be worked over. They’re innovative as all heck, but turning out deeply-flawed guns at the rate of five a decade is ridiculous.

        • RealitiCzech

          In a perfect world, Keltec would be the R&D lab for some larger, more QC-capable company.

          • Randy Vooty II

            Keltec isn’t the R&D lab for a larger, more QC-capable? Did you forget about the existence of Ruger? (There is humor in this post.)

          • TDog

            Randy: 1, Kel-Tec: 0

          • Giolli Joker

            …and then that company would be bought by Remington, to make it more profitable, and back to a non-perfect world at warp speed…

    • Phillip Cooper

      The real question is, what do you have against 10 year old girls, you sexist bastard?

      (I kid, calm down….)

      • TDog

        LOL. 😀

  • Squirreltakular

    I actually like the look of the Bullpup Unlimited stock. Might make my 20″ Mossberg a bit better for home defense than the pistol grip it’s wearing now.

  • GunbunnyGuy

    Lefties need not apply when it comes to the Bullpup Unlimited though…

    • Southpaw89

      My problem with every bullpup conversion, otherwise I would’ve tried one years ago.

    • BaconLovingInfidel

      Well of course liberals will be appalled, but the Bullpup Unlimited doesn’t really work for the left handed either.

  • Gabe

    I like bullpups but I often wonder if they would have the popularity they have if it were easier to get a SBR. Most of the issues that bullpups address can be had with a SBR or PDW and, in the case or a AR platform, much easier to train someone if they are already familiar with the full sized rifle.

    • Nick

      Simply not true. I have a SBR’d AR. It has a 10.5″ barrel. Despite having a shorter barrel, it is still 5 inches longer than my Tavor with a 16.5″ barrel. Longer barrel, shorter package, and better balance. SBR’s don’t hold a candle to a good bullpup.

      • BaconLovingInfidel

        Yep. With rifles, you’ve got to look at other calibers to reach equivalent utility and ergonomics/agility.

        I love both.

        I can’t wait for my first SBR bullpup. If Desert Tech’s MDR matches the quality of their previous designs, the MDR-C will be a wicked tool for ultra-CQB scenarios.

      • Gabe

        Just wondering out loud really, I wasn’t trying to state fact 🙂 I don’t own a bullpup so I can only speculate. They do seem like they would be harder to get used to due to the different layout but I suppose that can be fixed with a little training.

  • valorius

    I think i’ll just stick with my Winchester 1300 Defender. I use 2″ low recoil 1oz brenneke style slugs in mine. It holds 9+1 rounds with the factory mag tube.