Prototype RusEngin Bullet

A Russian inventor emailed me photos of his patent-pending bullet design. These bullets are loaded in 12.7×108mm cases.

The inventor did not explain to me how this design is beneficial but according to a study done by the US Military in the 1950s (PDF Link), the center of gravity affects how a bullets will yaw when it encounters a solid object. Yawing (and tumbling) can be reduced by make a bullet nose heavy.

Not long after that report was published both the USA and Russia adopted cartridges designed to tumble upon hitting the target. The 5.45×39mm round actually contains a hollow cavity in the nose to make it base heavy.

The benefits of tumbling bullets on soft targets is still hotly debated but for anti-material and anti-armour applications penetration is the name of the game.

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.


  • atlemt

    it seems like that bullet design could cause feeding issues in a semiauto.

    • Pete Sheppard

      To put it mildly; they might work in a single-shot rifle, where the cartridges could be chambered by hand–any kind of forced feeding would screw up the bullet’s alignment.

  • bbmg

    If penetration is the aim, I don’t see how it would be better than this:

    SLAP rounds not only boost velocity by having a lighter all-up weight than a full bore projectile, but due to the high sectional density after the sabot separates they retain their velocity for much longer downrange, and if you want to go deep high speed, density and hardness are what you want.

    Rather pointless to bass judgement without seeing the whole bullet though, what does the base look like?

  • Mouse

    I think it would be well stabilized during flight, and it looks like it would cause massive cavitation with that tip, but I don’t think it would go very far with that tip and tail shape.

  • Rob J.

    The bullet length could actually be counterproductive- small perturbations at the ends of longer bullets can actually accentuate yawing in flight, a simple extension of the principle of torque. Also, assuming he is not changing the mass of the bullet, it appears that the bullet’s sectional density is higher than a standard boat-tail at the center of the bullet, when viewed along its rotational axis. Having mass concentrated at the inner radius creates a lower rotational moment of inertia, which in turn reduces the stability at a given rotational rate. The bullet is potentially less stable along both transversal and rotational axes than a standard bullet. This design seems to not only be an answer to a question nobody asked – it’s also the wrong answer.

  • you do not need any tumbling in .50 cal / 12.7mm bullet; what you really need is a high BC and sectional density, and I could not see how it can be achieved with bullet of such shape.
    also, you must maintain existing max. COAL to be able to use ammo in existing mag- or belt-fed weapons of same caliber

  • Anthony H.

    I’d like to see what kind of effects this has against hardened targets. It should be intriguing.

  • gunslinger

    how is that held in at the end of the case? and if it’s not rifled, how will it maintain stability? or does it make contact with the rifling on the “outer edge”? if so will it spin correctly?

  • alannon

    Perhaps this is actually a submunition, intended to be mounted in a sabot like the penetrator of a SLAP?

  • Esh325

    “Not long after that report was published both the USA and Russia adopted cartridges designed to tumble upon hitting the target. The 5.45×39mm round actually contains a hollow cavity in the nose to make it base heavy.”

    Don’t all spitzer shaped rifle bullets yaw in flesh?

    • bbmg

      True, but only those with a rearward centre of gravity yaw visibly in the 12-24 inches of flesh available in a living target, hence this:

      • Esh325

        A 5.56×45 that’s supposedly designed to yaw has the chance of doing the same thing as that .303 bullet. Not every bullet yaws perfectly every time or yaws at all. You can see the 7.62×51 starts to yaw roughly at the 22 inch mark.

      • bbmg

        That 0.303″ bullet has a wooden nose, in order to shift the centre of gravity to the rear. If you look at the construction of the 5.45 bullet, it has an hollow space in the nose in order to accomplish the same thing:

        These are deliberate features designed to make the bullet yaw as soon as possible after entering soft tissue.

        If you look at the wound profile of a bullet that does not have this design consideration like the 7.62 x 39 steel core, you’ll see that it is possible for it to pass clean through a human target without yawing at all:

        The point therefore is that all bullets that depend on rifling for stability will yaw *eventually* in a fleshy medium, but for this to happen in practical situations the bullet needs to be designed with a rearward CG.

      • Esh325

        Yes, you’re right about that. You have to wonder did the Russians copy Yugoslovians since produced since the bullet design they used in the M67 also shifted the gravity reward to induce yaw.

      • bbmg

        Most steel cored bullets seem to have the lighter core at the rear and lead in the nose which would tend to prevent the bullet from yawing:×39%20Steel%20Core.jpg

        By contrast the M855 5.56 round has a steel nose and lead base, making it effective against body armour while still having a rearward CG, meaning it yaws to the extent that it destroys itself within the target.

      • Esh325

        If a 5.56×45 doesn’t fragment, then what does it do then?

      • bbmg

        Tumble 🙂

        Without the benefit of gyroscopic stabilisation, it’s what all projectiles with a centre of gravity rearward of the centre of pressure will do.

        Once a bullet enters a denser medium than air, the rate of spin reduces dramatically due to the increased friction and it is no longer sufficient to keep it flying pointy end first.

        Something like this which relies on fins as opposed to spin for stabilisation will zip through flesh without tumbling assuming the tail assembly remains intact:

  • FWIW: The report was published in January 1930, and reprinted 27 years later. Robert Kent was one of the plankholders at the Ballistic Research Laboratory, and is considered to be father of the Small Caliber/High Velocity cartridge experiments that surged after the Second World War.

  • Lance

    Like it but not really new technology. Looks like its can shoot underwater though;).

  • I’ll leave the ballistic discussions for those with the expertise – I don’t have that. That said, I do think that it would be extremely difficult to get a cartridge with a bullet of this shape to feed properly. I may be wrong, but I’ll wait to see one of these shot repeatedly until I believe it.

  • dan citizen

    This shape is not about yaw. These are super-cavitating bullets. They have distinct advantages when fired underwater (as in Russia’s newest APS which uses a small supercavitating bullet versus the old cartridge which was essentially a little spear) as well as advantages in range, wind tolerance and the ability to splash flesh in a truly dramatic fashion.