CapArms Quiet Shuttle System Tunable AR-15 Buffer

Capital Armament or CapArms is an Iowa based gun and ammo manufacturer more recently known for their $500 Titanium Magnum Rifle Suppressor (now $599). To compliment their titanium cans CapArms is now selling what General Manager Nate Rinehart is calling “an improvement to the traditional AR-15 carbine buffer system”, the CapArms Quiet Shuttle System.

The CapArms Quiet Shuttle System replaces the traditional Stoner carbine spring and buffer with a guide rod, smaller diameter shuttle weights, and smaller diameter springs. The shuttle weights act as the buffer and travel up and down the guide rod. The shuttle weights do not contact the inner walls of the buffer tube. CapArms claims this system eliminates the infamous “twang” of the traditional AR-15 buffer system. CapArms also says the system results in less erratic recoil and “by using a spring on a guide, there isn’t an undamped side-to-side vibration when the gun fires.”

The CapArms Quiet Shuttle System is tunable and features two different weights and two different springs, with the promise of more options in the near future. I would like to note that installation is not exactly drop-in and the system does require the removal of the standard buffer retainer pin and retainer pin spring.


You can buy the CapArms Quiet Shuttle System at and there is a quick installation video on the CapArms Facebook page.

Scott is a firearms enthusiast and gun hobbyist whose primary interest is the practical application of gun ownership. In addition to contributing to The Firearm Blog, he hosts and blogs for The Firearms Podcast, a podcast and blog about gun stuff by gun people. Scott is a 20-year veteran of the USAF and been a member of his base, state and the All Guard marksmanship teams. He can be reached via email at


  • PK

    Missing from this article – the price is only $99.99 right now, $139.99 MSRP.

    At that cost, it’s worth trying if you’re tired of the spring noise when running silenced but can’t justify the JP Enterprises captured spring assembly’s slightly higher cost. For $100, you even get two weights and two springs to try out, which seems like a decent deal.

    “The Quiet Shuttle System will not be retained by a typical buffer retaining pin, so the shuttle will eject upon removal of the upper. This is by design.”

    That won’t be too appealing to anyone in CA with an AR set up to tilt the upper open slightly for mag removal.

    • Jared Vynn

      The JP offering however is also available for ar10 and 9mm though with gen 2. It also can be used in carbine and rifle length tubes (using a supplied spacer for the rifle length).

      • PK

        True, and they’re extremely nice. Both systems are the same general idea, and this introductory offer (I assume) is a better deal for the whole set – for now. It’s good to have options!

        • Jared Vynn

          Options are always good, competition sparks Innovation and lower prices.

          • PK

            Just my thinking, along with how not every product works the best for every shooter. It really is wonderful how this hobby has a little bit of everything for every taste!

      • thedonn007

        You would need to remove the weight from the 9mm bolt carrier.

        • Jared Vynn

          The 9mm SCS from JP is newish and isn’t compatible like the ar15/ar10 models. No need to remove weights to get it to work, and 9mm buffers need to be heavier anyways.

    • Calling that ejection unappealing is an understatement. I don’t want to have to catch the shuttle every time I strip the gun down.

      JP’s system doesn’t have that issue.

    • Haulin’ Oats

      Tubb’s Flatwire Spring and Geissele Super 42 Buffer both solve the issue of spring noise and do it with less complecation and cost.

      • Sledgecrowbar

        I just ran a tubb spring for the first time this weekend and it does work to get rid of the sproing, but there is a very mild pogo stick-like sound of the spring rubbing against the inside of the buffer tube upon firing. It doesn’t break it for me at all, it’s great, although the price of these springs, while manageable, is still 7 times what a standard spring actually runs. At least it’s not 40 times the price.

        • Haulin’ Oats

          try covering your spring in grease, it should eliminate the pogo sound. Also try running a Spikes Tactical Tungsten Powder buffer weight with that tubb spring.

          • Sledgecrowbar

            It would be nice if there was a cleaner solution than grease. I’ve read about plasti-dipping the spring, apparently it holds up to the bending well and doesn’t mind solvents. I’ll be trying to with one of the pile of standard recoil springs I have laying around now.

          • Charles Applegate

            THAT is a cool idea. Let us know if it works!

          • Haulin’ Oats

            There’s a lot of variables here but it would be a safe assumption that a plastidipped spring could have an increase of friction over an undipped spring; which could affect reliability. Instead, I would try a dry lube like wax (coated spring & tube) or some similar material.

            Also plastic dipping your spring will defeat one of the main purposes of having a flatwire: the added material thickness will reduce its compressability and increased compression is david tubb promotes in his youtube video.

            You may as well just switch over to the JP Silent Spring or “DPM systems” and be done with it.

      • Qoquaq En Transic

        Anyone try using this combo to slow down a full-auto Shrike? Perhaps with a heaver buffer?

        Will this spring increase the power necessary to strip a round out of the link yet in combination with a heaver buffer show the Shrike ROF?

    • Rogertc1

      Like the spring noise hurts anything. Nothing in performance. In war you don’t even hear it.

  • JT303

    How loud is the ‘twang’ of a standard buffer spring anyway? Is it really that much of an issue? After all, even with this and a silencer, you’ve still got the noise of the action cycling.

    • PK

      Loud? Not overly, even with a can, unless subsonics are used. Annoying and bouncy? You bet!

      I also find it much louder if I’m wearing muffs instead of plugs, it conducts the sound better, and in that case the spring is primarily what I heard before fixing things.

      • JT303

        I see. Living over the pond means that I’ve lost out on a lot, but I’d certainly agree that most muffs do less to dampen the noise than plugs do. It might be something to do with the space between the foam and your ear that makes everything reverberate a lot more, but I wouldn’t know for sure.

      • uffdaphil

        My first shot with no ear pro (300BLK/Recce7) was so crunchy I though a bolt or spring had broken.

        The auto eject on cracking the upper makes this a no-go for me.

    • Haulin’ Oats

      Noise level depends on the AR. My sig makes almost no noise with the factory spring, where as the windham carbon src has the annoying twang and pogo sounds.

  • Marcus D.

    I like that buffer tube and stock–any one know anything about it? It isn’t on their site, although the spring assembly appears to be adapted for it.

  • mig1nc

    There’s at least four of these types of captured buffer system on the market now. I would love to see The Firearm Blog or somebody else do a comparison between them.

  • I got 99 problems, but loud buffer springs ain’t one.

  • mazkact

    I grease all my buffers,springs and tubes, no twang, no worries.Once greased and installed I rarely see these components again or think about them.

  • Julio

    There’s always someone, and this time it’s me: “To compliment their titanium cans”. Not “compliment”, but “complement”. Like “principle”/”principal”, these are words that any writer ought to double-check automatically.