Competition shooters like their bullets to fly as fast (and thus straight) as possible, and they try to keep recoil to a minimum. Italian ammunition-maker CompBullet produces a series of bullets of the same name, which are claimed to both go faster than normal ammo, and produce less recoil. The secret? The bullets have go-faster holes in them.
Available in several calibers, the copper alloy bullets have a main cavity in the base, with multiple "vents" machined into their sides. These reportedly serve several purposes.
First of all, when the gun is fired, the vents supposedly allow the propellant gases to go through the sides of the bullet, providing lubrication between it and the inside of the gun's barrel.
As the bullet exits the gun, the gases symmetrically shoot sideways out of the vents. This - so we're told - creates a "muzzle brake" effect. A muzzle brake is a device fitted to the end of a gun's barrel, that redirects the gases as they leave the gun, to offset the recoil effect. The vents in the CompBullets apparently serve the same purpose.
At the same time, the gases shooting out of the vents are also said to create a rocket-like effect, increasing the bullet's velocity. All of you physicists are welcome to weigh in on this one, but it's hard to say if gases exiting the sides of a bullet would really cause it to travel any faster than gases that were limited to pushing on it from behind.
Additionally, CompBullets are claimed to produce less muzzle flash and less smoke. If nothing else, all those holes probably make them lighter than regular bullets, to boot.
Source: The Firearm Blog
While those big shells use a slow burning powder charge to generate a large amount of gas, I\'ve thought they may also channel air from the front of the shell to the rear.
http://en.wikipedia.org/wiki/Base_bleed
The only time powder gases are pushing on the base of the bullet is when it's in the bore where we would find the holes blocked. Once the bullet exits the muzzle then a low pressure area is created at the tail of the bullet but there are no gases to create your rocketlike effect. You shouldn't need a physicist to tell you that.
In free-flight, there is the possibility that the low pressure area at the base will cause the small side holes to suck away the drag producing boundary layer air as well as serve as a base bleed to further reduce drag but I'd have to see proof of that.
A heavier projectile has greater surface area and therefore is more likely to be affected by a crosswind (windage) which would put it off target. Remember this is NOT about killing something its about putting holes in paper therefore loss of energy due to being lighter is not a problem - paper is not that strong.
Flow of gases exiting a cartridge is symmetrical providing the holes are CNC machined to be exact and providing the firearm is NOT damaged, this is a simple principle of pipe design and flow - relearn your physics, your thermodynamics and fluid mechanics. The hole in the base of the projectile is centered with the main axis of the projectile therefore the flow of gases WILL be symetrical.
Since when was 2500-2750 feet per second way to fast for a projectile. 2700fps is a very common speed for centrefire ammunition. Most competition shooters aim to get as high a velocity as possible as it flattens the trajectory which in turn increases accuracy.
John Simpson please understand this: Whilst in the firearm the holes in the projectile will NOT always be against the inside walls of the barrel, you forget that firearms have a thing know as rifling which is cut into the barrel so that the lands of the rifling are the only thing that touch the projectile, therefore there is space for the gases to escape in the barrel which will allow a muzzlebreak affect as the angle of the holes woulde vent the gas back towards the casing in the chamber of the firearm thus reducing the felt recoil.
Overall you guys commenting on this article have NO IDEA of exactly what happens inside a firearm. Feel free to check what I\'ve written here and provide sources that contradict the well know facts of Ballistics and Firearms Design.