Why Does Nobody Make An AR-15 Progressive Buffer Spring?

The guys at Strike Industries have been experimenting with buffer springs. They emailed me asking if I knew why nobody sells progressive buffer springs for the AR-15. I actually have no idea why they are not made.

Standard AR-15 Buffer Spring

Standard AR-15 Buffer Spring

Progressive AR-15 Spring

Progressive AR-15 Spring

A progressive spring is a spring that has a “variable rate increase throughout the spring’s working range.” In other words, the distance between the coils is smaller at one end but gets further and further apart towards the other end. This means it offers less resistance to a small force, but progressively more resistance as a greater force is applied. In the context of a car suspension spring, a progressive spring can respond to slight changes on the surface of the road while also providing a lot of resistance to a pot hole.

I cannot decide if this would have a positive or negative effect on an AR-15.

Can any of our readers tell us why nobody is selling progressive AR-15 buffer springs?


Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


  • Gunhead

    When in doubt, experiment.

  • Cristian

    I tried this with airsoft spring rifles,but just like you,i found out there are no such springs available on the market,so i just cut a different spring in half,and added it to the original one.
    To cut to the conclusion- the result was not as sattisfactory as i would’ve hoped….

  • Zapp Brannigan

    Hooke’s Law: F = kx. A linear effect plus(or minus) another linear effect is a linear effect. Two springs in series with different spring constants can be replaced by one spring.

    • <- What he said. The usual way to have progressive or variable rate is to have different coil pitches that allow sections of the spring to "close up" leaving only the remaining stiffer sections as it is loaded. AR buffer springs are so light gauge that they wouldn't stack nicely if compressed solid, would probably buckle and possibly bind with the buffer and tube.

      Multiple nested springs (parallel) with different engagement lengths are another possibility but you could end up with a noisy mess of loose springs unless you had a way to take up the slack.

      Long bump rubbers like silastos might work but could be too abrupt for something as fast as firearm recoil.

    • dp

      Right on, Zapp; you know your physics of materials.

    • Sadler

      A minor correction to Hooke’s Law: F = -kx. The force that the spring exerts is assumed to be in the opposite direction from its displacement.

      Another note: the description of a progressive spring is a bit off in the article. The rate varies throughout the entire spring, and is not simply held to “smaller at one end and further towards the other.”

      I also agree with Wielsucker. Progressive springs are meant to stack coils, and that’s difficult with lighter gauge coils, as they tend to buckle before stacking neatly.

      Has anyone experienced enough trouble with their existing buffer springs to want a different one? It’s possible that some loads may be hot enough to deform the spring, but I don’t think that’s likely, with conventional loads. Even then, you could just use a heavier spring. I don’t see any need for this idea, and it’s difficult to see who would buy it.

    • nadnerbus

      Is Hooke’s Law as hard and fast as Brannigan’s Law?

    • AcyclicDirectedGraph

      You all fail at the internets, and physics in general. A few minutes with google, and presto!



      and while not “progressive” per se:


      Also, I’d like to add that the timeline of innovations in the firearm industry vs those in almost all other mechanical engineering related industries is quite different. I’ll let you take a guess at which one consistently lags behind all others. 🙂

  • Troy Emge

    Most people who would be in the market for this kind of thing are already moderating their BCG cycle velocity via things like mid length gas systems, tailoring buffer weight, adjustable gas blocks and receiver extension type.

    • sauerquint

      I thought the pneumatic buffers did this as one of their debatable benefits.

      • Troy Emge

        I’ve never bothered with that, way too hokey.

  • J Man

    My guess, which is as educated as a layman can get, is that a progressive spring doesn’t do anything truly beneficial. The benefit of such a spring is to compensate for differing pressures. Even though different loads apply different pressures they all “dump” all of their pressure in a split second. It would stand to reason that given the floppy, sloppy, nature of the spring that it isn’t a high performance component so much as a force necessary to close the bolt. Also, with the high number of differing rounds it could mean faster cycling with some and slower with others, if the net effect means a similar average then why bother. There may also be functionality problems with some rounds which would, in my mind, ruin any advantage.

  • JT

    Progressives want to take away our rifles, not improve them

    • sauerquint

      Guns, not politics. Move along.

    • Icchan

      Would you rather a Congressive buffer spring?

      • derfelcadarn

        That would not work at all

        • Rusty

          Much like its namesake.

      • Blake

        Or an Arab buffer spring?

    • dec


  • Sid Collins

    The Bradley Port Firing Weapon uses three springs around a narrow buffer shaft to achieve a phenomenal rate of fire. But all that does is increase the rate of fire. There is no need for progressive buffering.


    Considering the military point of view, maybe its not used because it might add the risk of soldiers assembling the spring in the wrong way and causing malfunctions. In Bersa pistols (at least in a .22 I own) and GSG-5, you have to install the springs in a certain way if you want them to work OK.

    • dp

      On pistols it may make some sense, since you have right from start free coasting assembly unopposed by anything but spring (and buffer, if present). If the spring is progressively wound, it makes parts go to rest with little bit more of authority. But the design which would relay on direction of its assembly is incorrect.

  • bbmg
    • dan citizen

      sounds like a lot of hot air.

      • bbmg

        Definitely works, British firm Theoben have built their reputation as purveyors of top of the range air rifles on guns using this system: http://www.pomona-airguns.com/Theoben%20Eliminator.htm

        • Ramsey A. Bear

          Shock absorbers + spring. air or oil. just like your 4X4 truck. Pluses are you can get a real (pardon the term) progressive rate. The tube would also keep the spring from binding. Negatives would be weight gain. There are some ar-15 buffers that do some of this already.

          • Chase Buchanan

            Another negative would be price increase.

  • Kyle

    JP enterprises have a buffer tube sping assembly they make that rep lauded the original sprig and buffer.

    • Kyle

      Replaces not rep lauded lol IPhones and OS 7

  • Ian

    Mostly because they don’t work the way people think they do. With the exception of a coil binding spring (something you do NOT want in a gun), a “progressive” spring doesn’t differ at all from a constant coil spring with the same overall rate. The “softer” coils don’t collapse faster than the “stiffer” ones. The whole spring still flexes together.

  • dp

    Editor’s assessment is correct. Extent of this ‘creative contribution’ is next to none. It is also indicative of “AR fatigue” as accessory makers are disparate to scratch out any new idea to make buck on believing customer. Besides, what I see in picture is NOT progressive wound spring, but spring with two different pitches.

  • Dan G

    it has been stated already but variable pitch springs which is what it looks like is being talked about by the pics do not work better for this type of application. I am going to use airsoft as a reference because it has a nearly identical situation as AR’s and variable pitch springs are used there. Yes the initial impulse takes less energy but the follow on impulse takes more energy to fully compress the spring so In an airsoft gun it takes more energy to compress the spring and on weak motors or batteries the gearbox can bind up if not tuned right. In the Case of an AR 15 and its relatives this would mean that the gun would unlock faster but may not fully cycle to the rear on lower pressure rounds causing malfunctions which defeats the purpose of replacing working OEM parts.

  • Steve

    First poster hit the nail on the head – the bolt carrier travels in a fixed range of motion i.e. the same start and end point. A progressive spring would do nothing aside from increasing manufacturing costs.

    Sounds like Strike Industries needs to hire an engineer…

    • Steve

      Hmm, I guess I meant Zapp rather than “first poster”.

  • It strikes me that it might induce or aggravate carrier bounce during the feed cycle.

    • Mikey

      Actually, just the opposite. One advantage of progressive springs that nobody here has mentioned is that varying spring pitch (coils per inch) reduces or eliminates compression waves traveling back-and-forth through the spring (resonance). Both springs in the last photo have a section near the middle with a different pitch than the rest of the spring. I suspect this was done specifically to counter resonance.

      • Ian

        And spring surge has nothing to do with carrier bounce. Or anything else for that matter.

      • KC

        so it sounds then like they want to get rid of the springy sound

  • Some Rabbit

    I suspect it’s just a matter of goodenuff engineering. The current spring works good enuff.

  • Mark

    Just my uneducated opinion: Progressive springs are used on cars because not every bump you hit on the road will compress the suspension completely. The progressive nature of the spring allows it to absorb the small amount of movement without transferring shock to the frame. If you hit a large bump the suspension compresses all the way and the stronger end of the spring helps absorb the extra force. As far as I can figure, a progressive spring is only useful when you will be making mostly small movements with a few large movements thrown in. With an AR-15 all the movements of the bolt carrier will be full length and therefore a regular spring is probably cheaper and just as effective.

  • FightFireJay

    My understanding of springs comes from being a motorcycle mechanic. The two things that stand out for me are…
    1) Progressive wound springs only act progressive if they can properly coil bind, as it does in a fork tube or shock. I doubt these can, So they will act as a straight rate spring,
    2) The difference in coil windings will reduce harmonic vibrations it does in valve springs.

    How springs operate in a pistol it’s different i know, BUT a progressive spring would actually be counter productive. We want more spring tension at rest (preload) to keep the slide in battery and less tension at compression to keep the slide from rocketing forward at unruly speeds.

    This is part of the reason why guns with longer recoil systems tend to shoot smoother.

    (Also, most aftermarket springs for pistols SAY they have different rates, but really are just longer or shorter for more or less preload and they have the same spring rates.

    • FightFireJay

      Taking things one step further…my theory is that you would want a longer lower rate spring.

      The extra length would give the required preload and the low coil rate would reduce excess bolt/slide speed. Yep, make that spring as long as you can without prematurely binding.

  • GoofyStance

    Hey Steve, i’m kinda curious, how come no one on site has ever done a range review on those old hydraulic and pneumatic buffer tubes? Did everybody just dismiss them as novelty crap?

  • ArcRoyale

    It sounds like what they want to do is create a replacement buffer spring that acts like a constant recoil system. They want the spring to get progressively stiffer as it is compressed to slow the bolt gradually rather than having it dump all the velocity when it bottoms out at the end of the rearward stroke.
    I don’t know the physics so i don’t know if that is actually possible, but i think that’s the general idea.

  • Isaac FluffyWolf Rader

    That thing’s uglier than my last stalker, but I’m definitely impressed.

  • Tpa Gunslinger

    I happen to know for a fact that one firearm manufacturer in the Tampa area uses Progressive buffer springs in some of their firearms. Unfortunately, since it is not listed or mentioned on the website and is not common knowledge, I cannot disclose the maker.

  • freebug

    I think it has to do with timing. Since the progressive spring is variable in force, it affects the timing of the bolt. When used in an automatic weapon, this would cause timing issues and the need for the buffer to be “dynamic” in weight as well.

  • Johnny5

    It’s funny how technical and difficult some people are trying to make it when the answer is so simple. A “progressive” spring would offer less preload.