Vltor A5/HK416 Test Data

It’s hard to find a more contentious topic in the AR world than “piston vs. DI” – that’s why it’s nice to have some hard data to work with.

Vltor conducted testing of 10.5″ and 14.5″ HK416s, specifically, their rates of fire, both suppressed and unsuppressed – incredibly, the 416’s rate of fire with the stock buffer was as high as 1106 rounds per minute suppressed (10.5″), and 941 rounds per minute unsuppressed (14.5″). That’s incredibly fast, and can cause a host of issues – among other things, many magazines just won’t be able to keep up with such a high rate of fire. It’s also harder to control a weapon that cycles at that speed, either on full auto or semi auto.

For comparison purposes, a Colt M4 is designed to shoot 800 rounds per minute unsuppressed.

With the Vltor A5 stock system and its extra heavy buffers, however (5.3oz stock, 6.1oz A5H3 and 6.9oz A5H4), rates of fire decreased to more manageable levels – 788 unsuppressed, and 914 suppressed (with the A5H4). That’s a decrease of 187RPM for the suppressed setup. That’s an incredible drop, and will increase the service life of certain components while making the weapon easier to shoot. Interestingly enough, the HK416’s rate of fire (with the standard, non-A5 buffer system) is almost identical to some LWRC data that was recently posted on M4Carbine.net. Some other piston ARs have similarly fast cycling times.

If you want to know a little more about the A5, check out the video I made a few days ago –



Filed under Firearms

6 responses to “Vltor A5/HK416 Test Data

  1. Mike W

    Looks like an A5 may be in my future.

  2. Nathaniel

    This seems to indicate that, in order to make their piston ARs’ reliability match their claims, manufacturers have had to overgas the everliving undesired afterlife out of them.


  3. Redchrome

    The MGI rate-reducing buffer is known to have a substantial effect on rate of fire for full-auto weapons. More than the Enidine hydraulic buffer or an H3 buffer (no idea how it stacks up against the A5 stock buffers). Small Arms Review has used it several times in articles, and independently verified that with a 20″ full-auto AR15 the ROF can be as low as 550RPM.


    Nathaniel, all short-gas-system rifles are going to be pretty hard-cycling. Even DI ARs with pistol-length gas systems (needed on 11″ bbls) will run sometimes 1100RPM. Fundamentally all this stuff is way more complicated than most of us have the experience to understand; and the reason one gun cycles faster than another is much more complicated than ‘rifle A has a piston and rifle B does not’. An adjustable gas regulator (whether on a DI or piston gun) does have a lot of advantages…

    • ForwardTilDawn

      10.3, 10.5, 11.5, 12.5 barrels all use Carbine Length gas systems, not pistol gas systems. I own a 10.3in DD MK18, 10.5in Noveske, 11.5in BCM, 12.5in BCM upppers. All use Carbine length. 7.5, 8.5 barrels use pistol length gas systems.

  4. Redchrome

    thanks for the correction. I was misremembering where the usual cutoff was for pistol-length vs. carbine-length gas systems.

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