December 15th, 2011

From Italy, with Holes — The Radical Ported CompBullet

An Italian company, CompBullet, has produced a radical new line of CNC-machined projectiles with a cavity in the bullet base connected to ports (holes) placed radially around the bullet’s circumference. Currently CompBullet offers six bullet types: 9mm (100 gr), .40 cal (155 gr), .44 Cal (200 gr), .45 Cal (200 gr), and .30 Caliber Rifle (125 gr). CompBullet’s pistol projectiles have one row of radial ports, while the longer rifle bullets have two rows, resembling the porting on a muzzle brake.

CompBullet Ported Bullets

Italy’s CompBullet makes many claims about its new, patented ported bullets. Supposedly the ported, cavity-base bullets go faster than conventional bullets, yet generate less recoil. CompBullet also claims that its radical projectiles produce less smoke and reduced flash on exiting the muzzle. We are skeptical of many of CompBullet’s claims. We also have some concerns about bullet integrity and potential safety issues — at least when used in high-velocity applications.

Compbullet claims that gases exiting the radial ports “lubricate” the bullet as it travels down the bore, yielding enhanced velocity. However, if any gas is actually able to exit the holes while the bullet is in the rifling (it’s not clear that in-barrel venting really occurs), then this will simply serve to REDUCE the gas pressure pushing on the base of the bullet. If anything, the bullet should go slower than a conventional projectile, not faster.

CompBullet Ported Bullets

Jet Effect
CompBullet projectiles have a cylindrical cavity in the base. CompBullet claims that hot gases will shoot out the bottom of the bullet (like a rocket) and this increases velocity. But this runs contrary to the bullet-maker’s claim that the hot combustion gas moves forward and out the vents. But what, you might ask, if there are powder kernels that have migrated into the cavity and ignite inside the bullet? That might indeed cause gas to move both forward and rearward. However, the force of any rearward gas jet would be minimal compared to the main pressure flow pushing from behind, at least while the bullet is in the barrel.

Reader’s Comment: Hope the holes are small enough so the powder doesn’t fall out if the round is tipped over or something. It’s a good idea for custom salt and pepper shakers though!” –Josh

Recoil Reduction
Muzzle brakes reduce felt recoil and muzzle lift, on both pistols and rifles. However, they are attached to the gun. We’re not sure how gas blowing out the sides of a bullet is going to have any effect on recoil, because that action occurs after the bullet has left the muzzle. It IS possible that some in-barrel venting from the bullet’s ports may occur (if the ports aren’t blocked by the rifling), but that, as explained above, will only serve to reduce pressure pushing on the base of the bullet and hence reduce velocity. To the extent CompBullet projectiles deliver less felt recoil (if they do), it’s probably because they have lower velocity. If CompBullet projectiles actually fly faster (than do conventional bullets), that would be easy to demonstrate with chronograph tests. However, CompBullet provides NO CHRONOGRAPH DATA on its website. Without such data, we remain unconvinced.

Safety Issues
With a CompBullet projectile, there is the potential for powder to shift from the cartridge case into the bullet’s central cavity, prior to ignition. If this occurs, and the kernels inside the bullet do not fire off prior to the bullet leaving the barrel, there is the possibility of an explosive fragmentation of the bullet once it leaves the muzzle. We don’t know if this could actually happen, but there’s a word for a small, metal container filled with gunpowder — a grenade.

Bullet Integrity
A conventional jacketed bullet can fly apart when the combination of heat, friction, and spinning force stresses the bullet’s construction. With the CompBullet projectile, you have a bullet that is heated from the inside out, with numerous weakening holes drilled in the structure.

We discussed the effect of radial ports on a bullet with Bryan Litz, chief Ballistician for Berger Bullets. He said: “this ported bullet design is interesting, but I can’t see how it would have any usefulness for precision shooting. If flaming gas really jets out the ports, and the outflow of every port is not perfectly uniform, then this will quickly cause a reduction of bullet stability, which won’t help accuracy at all.” Bryan also wondered if drag from the gas out-flowing from the ports might slow down bullet spin-rate. With less rpm, spin-stabilization would be reduced. “Unstable bullets are not accurate”, Bryan added.

Flash Signature
There does appear to be some evidence of a smaller smoke “cloud” on bullet exit and a reduced flash signature, if the photos on the CompBullet website can be believed. We would like to see an actual comparison between conventional ammo and CompBullet ammo, using identical powder charges. CompBullet’s photos do not provide a comparison with ammo loaded with non-ported bullets. We cannot confirm that flash is reduced unless we can see photos of both ported and non-ported bullets, shot with the same powder loads, in the same lighting conditions. See sequence below with 9x21mm pistols:

CompBullet Ported Bullets

The inventor of the CompBullet ported projectile is Alain Della Savia, a IPSC Grand Master and 6-time Italian National Revolver Champion. He was inspired by the recoil reduction offered by ported handguns. He hoped to develop a new kind of ammo that had reduced recoil, while still satisfying the IPSC “power factor” requirements. His solution was to build ports in the bullets themselves, using CNC-machining methods: “After a year of experiences, [Alain] found the right balance between materials and internal compensation system inside the bullet.”

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