The Comp Bullet is a intriguing invention by an Italian firm of the same name. The bullet feature vents that, the company claims, increase velocity and reduce noise. Steve at The Firearms Blog writes:
Do you think they would work?
Link | Company Website
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. [...]
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?
Do you think they would work?
Link | Company Website
The Muzzle-brake effect would be accomplished by the gases escaping laterally as it leaves the barrel, similar to a normal MB.
The "Rocket Effect" I'm guessing is air traveling over the surface of the sides, through the outer ports, and then into the center and out the back port.
It appears to be flat-tail like a 30-06 round, and not a Boat-Tail, like a 308.
I'm guessing that the site + back porting would function similar to an under-tray+diffuser combo on a race-car, reducing the area of low-pressure suction/drag immediately behind the bullet, by channeling side-air into it.
They could possibly ~'tune' the size & edge-chamfer/belling of the side ports (like the end of a subwoofer port-channel) and same of the rear port to optimize this effect.
If they wanted to more precisely-direct differing port-paths, they could also machine the inside of the back port and create zones & guides appropriate to how much air they wanted to let in at what stage & how they wanted to channel it.
Ex: smaller ports up front, larger in back, perhaps with a center cone/velocity spike similar to the spikes in the front of the SR-71's engines.
The size/characteristics of these side ports and back-port interior treatment could be varied, depending on the amount of gunpowder each bullet was targeted for in the ultimate cartridge, concurrent with range, stopping-power, accuracy, etc.
Other than that, no ideas right now.
the exhaust is usually centered in the center 1/3-1/2 of the car laterally,
and pretty-much halfway between the uppermost rearward edge of the diffuser and the last trailing edge of the rear top surface/trunk-lid,
so that may also have influenced the vent-bullet designers' thinking, too.
Something about the company website just screams fraud.
These are pure woo! Probably.
The complete and utter lack of ballistic figures. If I invented and tested a super bullet, I would be telling the whole world what it could do.
This guy? About the only information is the bullet weight and diameter.
The firing demo videos show only someone firing rapidly with no appreciable recoil. Could be light loads or blanks. I'd be more impressed if he showed the target after firing. Not convinced anything even hit the target.