M443 Caseless Full Metal Jacket

The M443 5x23mm (.197 caliber) Caseless FMJ is a type of ammunition used by the UNSC in their M7 Caseless Submachine Gun. This ammunition is classified as "caseless," meaning it does not have a metallic casing surround the powder and sealing the bullet, propellant, and primer together. Instead of using this casing, the round uses a combustible adhesive to seal these components together. Because the chemical "casing" is vaporized when fired, there is no need to eject spent brass casings.

This feature is very beneficial. It reduces friction inside the magazine, one of the main causes of jamming in weapons. It also negates the need to expel casings, which also is a major cause of jamming, as mentioned above. This is important, as a user wielding two M7s at once would not want to have hot brass flying in his face from the eject port of the weapon in his left hand. The projectile itself is "jacketed," or coated, in metal (possibly copper or steel) to aid in penetration of the target. Caseless rounds are actually embedded into the block of propellant, reducing their length, allowing more ammunition to be stored in a smaller space.