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Benefits of the Cavity Back system

After much testing as well as consulting with industry professionals these are the benefits of the Cavity Back in small cartridges in gas operated firearms. Many of these benefits also equate to projectiles of any caliber with the Cavity Back system.

1. The cavity in the rear of the projectile allows for more room for a larger powder charge than a projectile with a typical flat, boat-tail or rebated boat-tail design. The cavity effectively increases the capacity of the cartridge case by typically .5 to 1.5 grains of powder weight determined by powder density and caliber diameter.

2. By increasing effective case capacity the cavity allows the cartridge to “breathe” better. Resulting in a slightly cooler burn and slightly less violent activity inside the cartridge case during propellant ignition. Also allowing for more powder before compression.

3. The area inside the cavity actually has pressure inside it just as an even pressure acts on the outside of the boat-tail. As the projectile exits the muzzle the gases are forcing their way past the projectile and into the air. Some call this “blow by blast”. It is fairly well known that these gases then pass the projectile and envelope it during the first part of its flight out of the barrel. It is known that a rebated boat-tail or a small conical area in the base of the projectile or a combination of the two can cause a projectile to be more accurate.
With the cavity back the gases are forced even more outward as the projectile exits the muzzle inhibiting the turbulence and allowing the projectile to “go to sleep” quicker resulting in a more accurate projectile.

4. The cavity system allows solid copper projectiles of the same weight as a lead based projectile to be loaded to the same cartridge overall length. It also allows it to be pushed to the same or higher speeds as the lead based projectile. This is true even though the solid copper projectile is longer in length than the lead based projectile.

5. Due to its particular shape, the bullet has its center of mass behind its center of pressure. When the bullet is in flight, the center of pressure always positions itself in the direction of flight, that is, with the tail pointed forward, pivoting on the point of pressure. If the bullet is not stabilized, these two forces acting together will cause the bullet to tumble. We can consider the distance between the center of mass and the center of pressure as a lever. The longer the “lever” is, the higher the destabilizing force it causes. Longer bullets, and especially bullet shaped with long ogives, have longer “levers” and thus are the most unstable. The Cavity Back shifts the center of gravity or center of mass forward decreasing the length of the “lever”. Enhancing the Dynamic Stability of the projectile.

6. Thorough testing has proven the Cavity Back smoothes out the pressure curve by creating a hemispherical powder containment chamber. As the powder burns and pushes on the chamber instead of a flat or dished bullet base the bullet starts its movement sooner due to the increased surface area. This lessens the pressure spike as the bullet enters the rifling.

Cavity Back Technologies LLC