Bullet + Compensator = CompBullet

The CompBullet is an interesting bullet made by an Italian company. The bullets, made from a solid copper alloy, have vents machined into them. According to the company, these vents reduce friction by allowing gas to lubricate the bullet as it passes through the barrel and then act as a muzzle brake as the bullet exits the barrel. They apparently also reduce smoke, increase velocity (a rocket effect as they leave the barrel) and reduce muzzle flash. In other words, they are miracle bullets.

The use of gas to lubricate firearms is not new. Many automatic firearms have fluted chambers to vent gas through the chamber and around the brass case to lubricate it during extraction. This could work for bullets as well, but would it help enough to make significant improvement in ballistics in a pistol length firearm?

As for the muzzle brake and “rocket” effect claim, the physics is beyond me. I cannot work out how gas venting out of the bullet for a brief moment in time would have any effect on recoil. Surely because the bullet is not fixed to the gun any muzzle brake effect would slow down the bullet not the recoil of the gun?

As for the claim that it reduces muzzle flash and smoke, again I don’t understand how it would make any difference. The company has photos on their website purporting to show decreased flash and smoke using the CompBullet compared to regular FMJ bullets. A single photo is meaningless, an ultra-highspeed video would be needed to make an accurate comparison.

That said, I would still like to try using one of these bullets. The company makes them in a variety of calibers and weights for pistols and .30 125gr rifle bullets.

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.


  • Lance

    yes but they would increase barrel wear and make it very expensive for ammo which is over priced right now.

  • Whatever

    If the holes aren’t machined to pretty tight tolerances, they have a good chance of causing a big drop in accuracy.

  • JMD

    Hm….several new factors that can affect accuracy. As if there weren’t enough of those before.

    If the holes aren’t located, sized, and aligned in an exactly symmetrical way, gas will vent unevenly from the holes, causing uncontrolled, unbalanced thrust vectoring that will push the bullet more from one side than another. Think of all the problems that can occur due to a malformed muzzle crown, then multiply them by the number of vent holes in the bullet. That’s the number of new things that could (and likely will) influence shot-to-shot consistency negatively.

    I have a hard time believing this will catch on as anything but a novelty item.

  • Alex-mac

    Those are speed holes in the bullets, they make them go faster!

  • Vhyrus

    The holes would have to be angled backwards to have any positive effect on the bullet at all, and I am fairly confident (although I haven’t worked out the math yet, its finals week I’m a little busy) that there would be no net gain over a solid projectile. That being said, removing material from the inside of the bullet makes it lighter. It doesn’t take a genius to figure out that a bullet with 20% less mass has 20% less energy and 20% less momentum. Adding weight to the front to compensate would either be impossible due to bullet dimensions or cause a seriously nose heavy condition that would lead to tumbling (not necessarily a bad thing but it would definitely affect long range ballistics). The part about the gas lubrication and muzzle brake effect makes sense, at least logically, although the gas would have to almost completely vent between the time the holes exit the crown and the tail of the bullet leaves the barrel (again, no time for the math). More analysis and/or independent testing is needed for an absolute decision, but from a cursory glance the manufacturer is making at least a few trumped up claims, to say the least.

    • JMD

      Your statement reminded me of something else. By creating bullets of a given weight and diameter with a hollow center (as opposed to solid), this design also sacrifices sectional density and ballistic coefficient, which will negatively effect long range performance.

    • Komrad

      I don’t think there would be any appreciable difference in recoil, even if there was enough gas vented in the short time the bullet is halfway out the barrel.
      It would vent the gas radially, like a flash suppressor, and would increase muzzle rise exactly the same amount that it decreased it.

    • TATim

      Of course, if the rocket effect does work then you wouldn’t have 20% less energy and momentum because v would increase although by my back of a napkin maths you’d need to increase v by a fair margin to get close to the same energy et cetera.

  • El Freddio

    Sounding a little BS that this would be useful. But then again, I’m an Armchair Commando, so what the hell do I know XD

  • Nick

    Correct me if I’m somehow wrong here, but if those bullets aren’t seated fairly low into the case won’t you powder charge dribble out the side of the bullet?

  • 18D

    It’s all a bunch of BS, A marketing gimmick trying too hard. Machined holes in the side of a hollow cavity is not going to change recoil impulse at all! The base of the bullet is the most important factor for accuracy. If there is a hollow cavity in the base, I would think accuracy would be negatively effected. This is just a day to take peoples hard earned money!

  • fred johnson

    Looks like an expensive idea that average shooters can never afford.

    • hojo

      It’s a clever idea to extract money from people with more money than sense.

  • MAJ Mike

    Interesting concept, but I’m no engineer and can’t really judge. However, would the holes in the bullets encourage their fragmentation upon impact?

  • MrSatyre

    I can see these making great conversation pieces on a bookshelf or coffee table, but that’s about it.

  • Ian

    There aren’t enough lols on the internet for this idea.

  • Hudson

    Did someone leave the Gyrojet drawings out again?


  • bbmg

    if you’re going to bother, why not fill them with power and bring back the Benelli CB-M2 caseless: http://cartridgecollectors.org/cmo/cmo07apr.htm

  • Since they are a “copper alloy” wouldn’t they fall into the new interpretation of armor piercing that the ATF has used recently?

    • Cymond

      I’m fairly certain that AP restrictions mainly affect handgun ammo. Additionally, AP is defined according to construction, not according to actual penetration capability. Supposedly, steel core 7.62×39 is restricted from import because of the common availability of AK pistols, but take tat with a grain of salt.

      There was a big flap a few years ago about some federal US law that threatened to redefine AP ammo as anything that can be fired from a handgun and can penetrate the lowest level of bullet resistant vest. Of course, handguns like the TC Contender mean that nearly anything can be fired from a handgun. You can bet the bank that .30-06 FMJ out of a 14″ Contender will penetrate a Level IIa vest. In essence, the law would have redefined most rifle ammo as AP handgun ammo, and effectively banned it. California almost passed a similar law recently. They attempted to ban solid copper rifle bullets. It would have had the additional effect of ending all hunting in the lead-free condor protected zones.

      Sorry for the political sidetrack, but it illustrates a point. Solid copper bullets are currently not considered AP or restricted in the US.

  • Doug

    I would give em a try, I cant imagine that most of the concerns about tolerance, and weight consistency have been dealt with. Id be skeptical of course, but they would be fun to try.

  • SKSlover

    it may not be the game changer that they claim, but its a new idea to a field where we need new ideas. (think 50yr old rifle designs still being the biggest part of the market)

  • Armed Partisan

    I got a couple observations: first, DRAG. Regardless of the benefits of the bullet design at the muzzle, down range, they will have tiny holes which will be pulling in air from the BASE of the bullet (which is already the most significant portion of drag on a bullet) as the very high velocity air flows OVER the holes. This might create vortices near the base which will in effect at like “super drag” on the bullet at long range. This, combined with the lower BC and reduced momentum will likely be significant.

    Second, long range is certainly not where this bullet will shine, as noted by several others already. The light weight will create a lower ballistic co-efficient compared to similar length bullets of the same caliber. That means the bullet will only work as well as a much shorter bullet while having less case capacity for any cartridge in which it’s used.

    Third, as noted by others as well, I feel that anything short of perfect alignment of the holes may cause stability issues as the holes vent. The holes are going to be in different locations every time the bullet is fired, meaning sometimes they’ll be on the lands, sometimes on the grooves. As the rifling is cut/swagged INTO the bullets surface upon firing, it means the holes are going to be bisected by rifling grooves and different heights. That means that the gas, largely equal pressure inside the bullet base at the muzzle, will have to travel different distances out of the holes, meaning that venting will actually begin sooner at some holes than others which might cause the gas to flow out of the shorter holes unevenly. I feel this will likely lead to erratic performance.

    Fourth, it’s well known that un-burnt powder escaping from the muzzle is a large source of felt recoil. This will likely do nothing to assuage that phenomenon. In fact, if the bullets do have a “rocket” effect as they are fired, such as that when the holes are vented at a backwards angle, it might even slightly INCREASE the felt recoil by forcing the gasses backwards towards the shooter. several muzzle break designs do this and make firing some rifles VERY unpleasant. The reduction in recoil is not worth the increased muzzle blast with some designs.

    Fifth, after the bullet leaves the muzzle, it’s torsional rotation is largely a factor of inertia. Will having “rocket vents” on the side of the bullet reduce that spin/stability?

    Many of these factors may be negligible, especially with pistol bullets, and they might actually work better than many of us anticipate, and if they do, I’m sure they’ll be around for years to come. Many people were skeptical of plastic framed guns when they first came out, as well as of small caliber, high velocity military rifles. Many of those people had to eat their words, and maybe we shall as well.

  • Dan-0

    Does it at least come with a complimentary bottle of snake-oil?

  • dg13

    Your explanation of the physics of the fluted chamber is not quite correct.
    You say: “Many automatic firearms have fluted chambers to vent gas through the chamber and around the brass case to lubricate it during extraction.”

    the first part is correct, but the purpose of the venting of the gas around the case is not “to lubricate it”. It’s purpose is to reduce the force that is caused by the pressure in the empty case causing it to expand onto the steel chamber. by allowing the pressure to get onto some of the outside of the case, you are reducing the effective area that the gases inside the case push on. Example: Gases inside the case push on 100% of the case outward, while gases on 30% of the outside of the case (in the flutes) push back-inward…counteracting 30% of the inward pressure, so you are left with 70% of the case pressure induced force outward.(percentages are just arbitrary). This reduction in force is what reduces the extraction friction. Basically, Int eh fluted chambers, the gases do not have a lubrication effect….they have a force reduction effect…..Not the same.

    Friction force is the normal force times the coefficient of friction. Your explanation states that fluting reduces the coefficient of friction, but actually the fluting reduces the normal force, not the friction coefficient.

    These bullets actually may have more friction force, since the pressure can get inside the bullet, and force the sides of the bullet out into the barrel during shooting.

  • Bryan S.

    Cool, whistle bullets!

    (for whistle pigs?)

    • lucusloc

      wooo! that’s exactly what i wanted for the 700 wtf! make it scream like a banshee and im sold, accuracy and ballistic considerations be dammed.

  • Robert

    They forgot to paint them Black, that would increase their performance even more! None of their claims pass the smell test, but Mall Ninjas will buy them by the case šŸ˜‰

    • mosinman

      hellz yah guyz! i found thesez bullitz that go faster! and reduce recoil! now to load these babies in my tacticular AK’s CLip with 11 pounds of lasers, lights, scopes, redots, and 2 fake suppresserssss

  • West

    If they wanted the bullets to go faster then they should have just painted some racing stripes on them.

    • hojo

      nonsense, the way to make them go faster is to put a really loud coffee-can-sized “muffler” on them. šŸ˜€

    • Red wuns go fasta

  • Rob

    I call bologna this seems like someone trying to make the next greatest innovation on firearms tech since the spitzer bullet.
    It’s like those people selling Zombie rounds, if it wasn’t for the absurd amount of people beleiving that’ll happen and they need specific bullets for dealing with them they wouldn’t sell at all.
    A no from this plinker

    • Rob

      Nebelkugel anyone? šŸ˜›

  • Ryan

    Ok to sum up
    These guys have changed:
    1: The gas dynamics of the interaction of the bullet with the gas expansion zone at the end of the barrel…
    – But nobody truly understand the gas dynamics of a bullet entering the free stream at super sonic speeds (many things start to work backwards from the way we think they “should” when you go to compressible flow).

    2: The weight and ballistic aerodynamics of the bullet in flight…
    – Manufacturing tolerances on a small bullet with that many holes would be variable to say the least. But again super sonic rotating bodies don’t act the way we think they “should”

    3: Only using solid projectiles…
    – Few people understand the non linear effects of a deformable projectile as it enters a target but usually solid projectiles don’t have a lot advantages.

    There is only one way to solve all these unknowns… I’ll need to test a 1000 rounds in each of several different sizes šŸ™‚
    All in the name of science!

    • Matt Fulghum

      My lab works with high speed flows and we’ve taken a whole lot of shadowgraph videos of gunshots, and I totally agree that there’s some interesting dynamics occuring at the interface right when the bullet has left the muzzle.

      On that note, however, I can say without a shred of doubt in my mind that these CompBullets are snake oil. The time scales involved are insanely short for the dynamics that would have to occur for them to do anything… microseconds!

      Long after (relatively speaking) the bullet leaves the barrel, there is still significant pressure inside the barrel, which leads to a compressible jet out the muzzle. Compensators revector this jet to produce reaction forces that help to combat muzzle movement, and act over the period of milliseconds! Several orders of magnitude longer than this bullet ever could.

      Also, I have a feeling that the increased velocities they see with these bullets come from the fact that they are solid copper, which is less than half as dense as lead!

      • Sean

        From the photographs, it’s clear that what the porting is intended to do is vent escaping gas sideways as the bullet leaves the barrel, in the same manner as a muzzle brake. However, given the speed of a bullet as it is exiting the barrel and the relatively tiny distance betwen the porting and the base of the bullet, I can’t see that this would provide any significant change in the flash and smoke; since the smoke and flash leaving the barrel normally expands in a cone downrange, the ports on the bullet venting the barrel perpendicular to the line of the barrel would _increase_ the perceived diameter of the flash and smoke, although the redirection should, by spreading the flash and smoke more rapidly, make them _perceptively_ dissipate faster and reduce the perceived intensity, even though no actual reduction in the overall _amount_ of flash or smoke is achieved.

  • Gso106

    I feel the need to correct some of the assumptions here stated here. First the statement about a 20% lighter bullet having 20% less energy and momentum is only true if the velocities are equal which they will likely not be. A lighter bullet will typically have a higher velocity and the relationship of velocity and energy is not linear (aka the velocity will not have to be increased 20% to compensate for the energy lost due to a 20% reduction in mass KE=1/2 * m * V^2). The momentum will be decreased although Iā€™m not sure when momentum is used in terminal performance. Additionally it is a common misconception that higher energy means better performance…what is important is how the energy is utilized and transferred to the target. Using their .30″ projectile as an example…A 125gr round loaded to the same pressure as M80 (147gr) using the same powder will yield more energy (although it is close) but that doesn’t mean the 125 gr will have better or worse armor penetration (dependent largely on ogive shape and material)

    Secondly a nose heavier projectile will not cause tumbling as moving the CG forward causes an increase in static stability. If you added enough weight to make the projectile actually nose heavy…there are only problems with dynamic stability and that is dependant of spin rate. Additionally as mentioned above it is unclear what effect the vents will have on spin damping although i assume the effect will be small enough that it will not effect stability.

    The gas jet effect is counterintuitive. Even if the gas could vent prior to the exit of the tail the effect would be increased recoil. The force would be between the muzzle face and the projectile (accelerating both the projectile forward and muzzle face rearward) increasing recoil.

    The only potential benefit I can see with these is decreased base drag due to the ability of the vacuum usually found at the base of the projectile to be filled with air from the vents. This will affect the boundary layer on the body of the projectile and may shadow the effects of the boat tail, however a net decrease in drag is at least possible.

    More Misc. Corrections

    It is common to assume that a decrease in weight means a decrease in BC, but it is impartant to note this is only true within the same exact geometry. A lighter bullet with lower drag can have a higher BC than a heavy bullet with higher drag.

    I am unaware of any research performed to date that shows evidence that the base of the projectile is the most important for what is reffered to above as accuracy (really what is meant is precision). there has been work showing that ogive shape may be related however that is in reference to how well the projectile “self aligns” with the bore during engraving. The only evidence for this claim that i am aware of is the concentricity of the boat tail, but that is a geometric tolerancing issue and exists on all features of the projecitle not just the base. there has been mention of rebated boat tails and the uncorking effect of the base of the projectile effecting accuracy however i have not seen any work to prove this.

    overall i think most of the manufacturers claims are not true, there is potential the drag reduction to work, whether there would be a performance increase or not is a question that will remain unanswered until testing is performed.

    • Vhyrus

      I went through a quick calculation just now and here is what I found:

      IF the bullet and casing dimensions are not significantly altered, we will assume equal amounts of powder in each which means equal initial force. Since F=ma, an equal force with 80% mass gives 125%acceleration. Assuming constant acceleration of the bullet from equal length barrels, this also gives a velocity of 125%. This means an equal momentum between the two bullets (since .8*1.25 = 1) but a kinetic energy of 125% (since K=.5mv^2, velocity is more important).


      The new design has a larger interior dimension, thereby changing the burn characteristics of the powder. Since pressure and volume are inversely proportional for a given temperature, increasing the volume in the casing decreases the pressure, which would also decrease the force on the bullet (since pressure is merely force distributed over a surface area). There would also be velocity lost to the gas pushing out of the vent holes against the barrel perpendicular to the direction of work. If the holes were angled backward that would help, but not completely solve the problem.


      Force would NOT be equal, and the above calculations would NOT hold true.


      I am an engineer and I say the bullet is weaker.

      • Gso107

        your calculations make an incorrect assumption that the powder charge is equivalent…with a lighter projectile the burn rate can be adjusted to not allow the maximum pressure to be exceeded which is what is the limiting quantity. Therefore if you redo your calculation you can likely squeeze a little more performance out of the lighter round. Also while invite the holes would allow minimal leakage and increase the volume slightly which would be in the noise of the system performance.

        FYI I am also an engineer…a ballistics engineer for the us army research lab and I do most of the ballitics work for small arms…any more questions and I’ll be happy to answer them

    • armed_partisan

      There will NOT be a decrease in base drag on this bullet design. When air flows quickly over the holes it will flow into the void in the base of the bullet and create a vacuum inside of the center hole, which necessarily has to be deeper than the holes if for no other reason than manufacturing tolerances. The air flowing rapidly over a boat tail design creates a vacuum that causes the base drag of a conventional target bullet, and by dramatically increasing the area for this to occur, it will increase the drag significantly as well. What’s more, the air is essentially running into a “flat” wall on the inside surface of the hole, in effect creating little spoiler flaps that will slow the bullet down. The holes are not going to create a region of higher than atmospheric pressure to over come the increased surface area that will create more drag. The internal void will create a vacuum, and that will increase drag.

      • Gso106

        I don’t see how you can confidently say there will be no drag reduction without testing…there is already a vacuum on the base of the projectile which is dependent on the area of the base…which the holes effectively reduce by allowing access to the free stream. I agree they may act as spoilers to the to exterior flow which is why I said the boat tail effect may be shadowed…I still feel that it is “possible” a net drag reduction could be the net result…I contacted the company and they responded saying they couldn’t supply round to a foreign country at this time, however I will be manufacturing similar designs and testing them in the next year and if I can get security to clear the results I will share them at the time.

    • W

      here is a way for drag reduction to work: boat tail ammunition šŸ™‚ without the expensive, time consuming process of machining out even holes for the supposed “rocket” effect to occur (which i conclusively believe is a bunch of bull). Correct me if I’m wrong, but should there be no improvement in accuracy or ballistics since there are minimal differences between this bullet’s base area and the base area of any other one? I can understand how a boat tail round works, by basically reducing the drag, but fail to comprehend how the mythical beast known as the “rocket” effect occurs with this new bullet…

      as far as the reduced recoil and muzzle flash goes, i remain extremely skeptical.

  • mosinman

    if you want the “rocket effect” on your bullets, bring back the gryojet!

    • W

      on that note, i was thinking “base bleed” rifle rounds for accomplishing the “rocket effect”. Perhaps the Compbullet hopes to achieve the “rocket” effect without a engine.

  • John Doe

    I don’t quite believe them. They ought to buy me some free guns and send me a couple thousand free rounds šŸ˜›

  • With all that machining and such, how much do these marvelous bullets cost, per each?

    Store bought, jacketed bullets cost enough – over 20 cents a piece to the best of my memory. (I just bought some 140 grain HP jacketed bullets for .357 Magnum – I think they were about $22.00 excluding taxes.) Cast lead bullets run in the range of 15 to 18 cents each.

    These are going to have to be pretty costly. Are they worth more than conventional bullets? Are they worth ‘x’ percent more than conventional bullets?

    • Bob

      I’d have to say that any full-up ammo that included these “wonder bullets” would be specially priced and therefore not for plinking at cans or paper targets. Like my use of Hornady Critical Defense ammo, I put those in my mags while I’m carrying, otherwise they get removed for when I use ball ammo at the range. If these compbullets do what the manf claims, I’m interested. For long arms, I’d be very interested if there is any substantial range/accuracy increase.


      • Bob

        I’d also add that a long time ago some German claimed adding grooves/lands to his musket barrel magically increased his weapon’s accuracy… the proof be in the pudding… let’s give them a chance to prove themselves before we scoff at their claims.


  • tincan

    I’m not adding anything to the conversation, other than to say that the quality of the comments on this site keeps me coming back. A lot of you know way more than I do about this stuff and it’s great to read what you have to say (esp you technical experts).

  • Komrad

    Easier to make a necklace out of.

  • Just to satisfy my prurient curiosity, I asked the company the price of the bullets. They replied – very quickly – as follows:
    [quote]Hello Mr. Montgomery

    We are sorry but we can’t sell products to foreign country

    Thank you

    Alain Della Savia

    So much for that.

  • W

    whats interesting about the website is that the inventor demonstrates how controllable a 45 ACP is with this wonder bullet


    oh that he is a competition shooter…

    But i’m sure there were proper controls in place to support the hypothesis… (LOL)

  • Philippe

    I’d like to see comparisons with full bullets of the same weight. I’d say a lighter bullet would indeed go faster (holes or not) and thus exit the barrel faster. Then more power from the expanding gases would be lost at the muzzle and felt recoil would be lower.

    The website is pretty low on details…

  • Bwhahahaha

    This company will be producing bullets with built-in baffles next so suppressors are no longer necessary.

  • Bill

    Well… any woman will tell you it isn’t just speed.. Weight, mass and expansion is more important!

  • Rick

    Reminds me of the “golf ball dimpled” bullet… An early April design.

  • KevinTheCynic

    Anybody else have flashbacks to the Gyrojet firearms?
    (From memory, the Gyrojet ammunition had its propellant in the projectile rather than in a separate case so the effect won’t be quite the same)