AR-15 Bolt Carrier Bounce

Andrew from Vuurwapen Blog has created this slow motion video demonstrating AR-15 bolt carrier bounce. It shows how lighter weight buffers allow the bolt carrier to bounce back after hitting the barrel extension.

The weight of the buffer becomes critical when said items begin to reach the end of their lifespan (or were never satisfactory to begin with), or when the weapon has been fired for thousands of rounds without any lubrication, or when various types of ammunition are used.

I highly recommend reading Andrew’s blog post.

[ Many thanks to jdun1911 for emailing me the link. ]

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.


  • Konrado

    5.45 x 39 AR-15? O.o Is there any info about this gun, especially any comaprisons to standard 5.56 x 45 AR-15s??

  • DavidR

    from the blog:

    “The AR-15 platform is great due, in part, to its modularity. However, this modularity also allows inefficient combinations of parts to function with one another. By understanding how each component affects overall function, the last .01% of reliability can be achieved, and recoil characteristics can be improved.”

    so very, very true.

  • larry weeks

    looks like both the lightest and heaviest bounce, the 3.9 didn’t. Nice job of showing the differences.

  • Tuulos

    Maybe it’s just me but I could swear the 5.5oz 9mm buffer bounces back too while the 3.9oz BCM H buffer is the only one that doesn’t bounce back. And wouldn’t the spring behind the buffer have a bigger word to say in the bounce than the buffer itself?

  • Lance

    Shows that you DON’T mix parts with other ARs stay with the mil spec parts with your gun or the parts it came with.

  • High speed cameras are amazing. It’s pretty neat to see what things do when their motion is caught on a high speed camera.

  • spudfiles

    It’s good to see that the proliferation of affordable and reasonable quality high speed cameras ( namely the casio series ) allows average people to take a critical look at situations that were hitherto unobservable.

  • Freiheit

    How would one detect carrier bounce without a high speed camera?

    “Shows that you DON’T mix parts with other ARs stay with the mil spec parts with your gun or the parts it came with.”

    But what if you’re building your own? Or if one you bought came with the wrong spring? Even if you don’t ever fiddle with the workings its important to know whats there and know how it should work.

  • Heath


    There are a bunch of great forums dedicated to ARs out there. and are two that comes to mind. And many of the better businesses that sell AR components are more than happy to help over the telephone to answer any questions you may have and to insure you get the correct parts.

  • jdun1911


    You don’t. You need a high speed camera. Bolt bounce isn’t limited to the AR. It’s in every auto rifle. Basic physic.

    Nothing wrong with mixing parts. Everybody doing it including the manufactures. They get their parts from other manufactures to built their AR15.

    Commercial or mil-spec is a non-issue for the average shooters. I have both version and I run both hard without any problems.

    Bolt bounce comes into play if you’re running SBR, running it hard, or burst/full auto.

  • jdun1911

    For those that are interested in upgrading to H Buffer and extra power springs and wants to know where to get them.

    I have bought from all of the shop listed below.

    Springs. Make sure you know the difference between rifle (non-collapsible stock) and carbine (collapsible stock).



  • Redchrome

    As for why the 9mm buffer bounced when lighter ones didn’t; it’s because the 9mm buffer is solid and does not have separate weights inside it. The sliding weights act like a dead-blow hammer to reduce bolt bounce.

    Notably, the rifle buffer didn’t seem to bounce much with any ammo. Note that the rifle buffer has 5 (steel) weights inside it, unlike the stock ‘carbine’ buffer that has only 3.

    The stock buffers use rubber bumpers between them, so they can move a *little* bit when the buffer impacts something. I would like to see a comparison with the MGI rate-reducing buffer which AFAIK uses a spring between the body and the weight, so more movement should be available.