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CompBullet: New Projectile Claims to Act as Muzzle Brake, Increase Velocity

There’s news that an Italian company has designed a new projectile that (they claim) will reduce recoil and speed up the bullet without any changes to the rifle itself. How, you ask? By drilling a channel in the center of the projectile and venting gasses from ports drilled in the sides of the bullet. According to the manufacturer these vents will not only act as a muzzle brake but will also make the bullet faster, as the channels are pointed backwards in an attempt to get some extra speed out of the round. I call bullshit, and here’s why:

“Rocket propelled” projectiles are nothing new. Fans of the James Bond series of films may remember a certain firearm from You Only Live Twice that used rocket propelled projectiles instead of the traditional gunpowder and dumb projectile used in firearms. Turns out that was a real gun being designed and produced with the hopes that the U.S. military would pick it up for the Vietnam War, but they were so expensive and inaccurate that the guns were quickly abandoned. The best groups they could get out of the gun was 17 MoA, which is over 1 foot at 100 yards.

One of the reasons that the gyrojet didn’t work is that the forces acting on the bullet after it leaves the barrel weren’t perfect — one port of the rocket engine would often be blocked or the exhaust would be impeded such that the projectile would inevitably fly off course and group worse than a CAI Tantal.

These bullets suffer from the same problem. Even if — IF — their manufacturing process was so accurate and precise that they could cut identical ports symmetrically around the projectile the act of firing the round and gripping it with the rifling in the barrel would inevitably create different sized ports that would vent the gasses in different directions. Even the slightest of imbalances in force would throw these rounds off course, or at least destabilize them to the point where they tumble instead of spin.

And then we get to the recoil compensation argument, which might actually be plausible. As the bullet leaves the barrel there is a fraction of a second where the ports on the bullet are exposed but the base of the bullet is still engaged in the rifling. At this point the expanding gasses driving the round can escape through those ports, but there isn’t enough space for all of the gasses to leave. This, in theory, increases the time it takes for the expanding gasses to leave the barrel and should reduce recoil as recoil is a function of force over a period of time (the longer it takes the gasses to leave the gun the lighter recoil will be). But that recoil reduction period is so brief and comes at such a great cost (reduced accuracy) that it really doesn’t make sense to use this projectile instead of attaching an actual muzzle brake (which will significantly reduce recoil).

In other words, no matter how well these things are made the concept itself is flawed. I think.

The icing on the cake? These are technically “armor piercing” rounds according to the ATF so we’ll probably never see them imported in the US.


  1. avatar Dirk Diggler says:

    FIAT anyone?

  2. avatar dls56 says:

    I agree that the likelihood of these bullets being very accurate is very questionable at best.
    Once again a fix for a nonexistent problem.

  3. avatar Chaz says:

    … channels are pointed backwards in an attempt to get some extra speed out of the round.

    The Comp Bullet folks need to publish some actual results. This might give the equivalent velocity boost of an extra quarter inch of barrel length.

  4. avatar Ben Eli says:

    I still want to see some footage of one of these leaving a barrel from a high-speed. Anyone else thinks it is kind of funny that a camera that is almost always played in slow motion is called a high speed? Just a tad ironic.

    1. avatar Mr. Lion says:

      It’s called a “high speed” camera as its shutter (and film, when used) runs many times faster than normal, even though modern cameras of the sort no longer have an actual shutter. While a conventional camera runs at 24 frames per second, high speed cameras run anywhere from 120 to billions of frames per second.

      The result is “slow motion” footage, though the camera is indeed running at “high speed”. I remember some of the older film-based high speed cameras, which were truly terrifying to sit beside while the thing spooled up to some ridiculous film speed.

  5. avatar Tarrou says:

    I’d love to see the physics on how venting gas early makes the projectile faster. I don’t care how you angle the ports, venting the propellant does not increase velocity.

    1. avatar racer88 says:

      You won’t see the physics of that happening, because it violates basic Newtonian physics. For each action there is an EQUAL and opposite reaction. And, a bullet flying out of a rifle is a perfect example of that. These guys want us to believe the vents will create a INCREASED and opposite reaction? Nope. Physics negates that.

      Muzzle brake effect? Ummm… negative on that, too. It has to be attached to the muzzle / barrel (and stationary) for that to happen.

      1. Any Muzzle Brake benefit would by simple math mean a reduced velocity, correct? Unless of course there existed a large qty of unburned powder which could be remedied by either a reduced load or a longer smoke stack.

        I see no benefit and only a detriment. Gases at the crown will make or break accuracy.

  6. avatar Mr. Lion says:

    Even if they are machining a venturi into the projectile, a series of axial holes aren’t going to feed it with enough air to produce thrust. They’re just going to create drag and slow it down. Else, if the suggestion is that gasses from the round are going to feed through these holes for the tiny fraction of a second the holes are exposed and the base of the bullet is not, and increase velocity to a meaningful degree, they need to put down the crack pipe.

    The muzzle break concept is sorta plausible, but it’s a solution looking for a problem.

    Plus, there’s no way you could cast something like that, so– individually machined bullets? A bargain at $20 each!

    1. avatar Tom says:

      Sort of what I was thinking…these bullets have to be very expensive.

  7. avatar Eb says:

    Frankly, what’s the point? Assuming the claims are correct, how much recoil and kinetic energy can you really gain from this? From a .mil perspective, you’re looking at calibers covering 5.56, 7.62, or .50; if you can’t handle the recoil from the first two you need to go home and suck on a nipple. Assuming you have the claimed velocity, the weight and bullet composition are probably the same; the “added” kinetic energy+bullet+target= not much return on your investment. If you’re looking at armor piercing this is entirely different but who in their right mind is going to take on a T-72/BMP with an armor piercing rifle/machine gun?

  8. avatar Ralph says:

    Whoopie, a new bullet. The count is now 23,972,648 major varieties and calibers with a mere 6,352 wildcat loadings and cartridges.

    Am I wrong, or is this a form of ballistic masturbation?

  9. avatar Gossven says:

    What is the point of the videos on their website, all those really prove is that whatever shooter they’re using can put an entire magazine into a steel silhouette target really quickly. They don’t show where the shots are actually impacting, if he was shooting a shoot-n-c target or something similar and one giant ragged hole appeared in the target that might actually show something.

  10. avatar Pete says:

    “According to the manufacturer these vents will not only act as a muzzle brake but will also make the bullet faster.”

    Why not just install a muzzle break on the rifle and reload your ammo to achive a higher velocity? Or is that too low tech and lacking in ‘newness cool’?

  11. avatar NR says:

    If you took one of these rounds, turned it upside down and shook it, wouldn’t the propellant come out, like a saltshaker? Any sort of wadding to prevent that would kinda defeat the whole point.

    1. avatar Art says:

      If this ‘bullet’ were seated into a casing with the holes exposed and without some sort of wad, then yes, the powder would flow loosely through all the holes. However, if the ‘bullet’ that we see in these pictures were seated in the casing, wouldn’t the holes be covered by the casing preventing the salt shaker effect and likewise causing expulsion of the projectile by gas pressure? Or maybe not, as you assume, the holes may be exposed. If that be the case, and there is no wadding, this projectile wouldn’t fly any further than a person could heave it, because there would be too much loss of propulsion gases, and it wouldn’t cycle in semi-autos without some serious action reworks (would be similar to subsonic .22 ammo). Would have to see specs on loaded casing to be sure of how the bullet is seated. Just making assumptions based on past experiences.

  12. avatar Gabba says:

    it’s ridiculous, the theory is flawed on it’s face. the bullet is not going to retain significant pressure after it leaves the barrel and with such a small volume to carry pressurized gas it just won’t work. but maybe it’ll sell like those “drive your car on water” gizmos, idiots buy enough of those to make a few people rich.

  13. avatar frankgon4 says:

    I agree that the theory is flawed. Wondering why they would market them. They have to have shot them. I still would like to see a video of these being fired.

  14. avatar Dean Anderson says:

    The gas pressure behind the projectile that is vented to the sides of it will act as a lubricant, creating the effect of a high pressure linear bearing.
    This principle is used in various applications including the draw & iron dies used to for producing aluminum cans, and air bearings on ultra precision measuring devices. I can see how the velocity can be increased with this “greased” projectile, accuracy & recoil, maybe, as the projectile clears the muzzle, the vented gasses will escape perpendicular to the path of flight.

    1. avatar Dennis Hannick says:

      Yes and mid-body obturators on projectiles are a good idea, too. Not.
      In fact, the hole in bottom of the projectile will not let enough pressure get to the side holes, before the pressure wave gets to the side holes and negates any pressure effect.
      In case you are wondering, I watched this silly idiocy get tried by the navy in one form or the other, several times. It never worked.

  15. avatar jd says:

    For the non-threaded barrel states [if it wasn’t technically AP]?…and with a pricetag to match all the special regs stuff in those states (‘green’ ammo, steel shot, no lead anything, buy only over counter retail)..Really is a non solution to a non problem for most of us.

  16. avatar Larry Arnold says:

    I don’t remember much about the GyroJet’s accuracy, as its other two problems overshadowed everything.
    1. The part you expended, the ammo, was expensive so the part you reused, the gun, could be cheap. Backwards.
    2. The rounds didn’t reach effective velocity until well past 7 yards. IOW they were wimpy precisely where you were most likely to need punch.

    Probably why John Browning didn’t invent it back in the 1890s.

  17. avatar people2me says:

    FRET NOT! The Proof is in the pudding… wait for the vid & stats, thats all… no use ‘expounding’ any further.

    In other words: NO VERDICT YET! The jury’s not in.

  18. avatar Jacob Blackburn says:

    If anyone has a copy of “Hatcher’s notebook” by MAJGEN Hatcher, you’ll see a similar idea that was tried in the early 1900’s. When then COL Hatcher was in charge of the army ordence corps they showed it didn’t work then either.

  19. avatar Don says:

    I pretty much agree with foghorn’s theory and conclusion. Keeping in mind I am not an aerodynamicist (at all), I think that those holes will likely create airflow separation to occur before the back end of the bullet (laminar flow over the bullet kind of ‘sticks’ to the surface, separation is when it unsticks creating turbulence.) The turbulent flow on around the back half of the bullet could either destabilize it or at least create a low pressure region at the back inducing higher drag. I think ideally you want the flow over the bullet to be such that the low pressure region happens well behind the bullet. Maybe. Or I could be getting all of this backwards.


  20. avatar Anon says:

    The main problem with the gyrojet was that rockets need a while to build up speed. At close range, the rocket wouldn’t do anything. You could stop this gun at point blank with cardboard. You could stop it with a finger. Coupled with manufacturing problems with the ammo, anything you could hit reliably wouldn’t be injured, and anything far enough away to be injured couldn’t be hit.

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