The HK 4.6×30mm cartridge is a type of ammunition used in the Heckler & Koch MP7 Personal Defense Weapon (PDW) and by the canceled HK UCP pistol. It is an indigenous German cartridge. It is designed to minimize weight and recoil while increasing penetration of body armor. It features a bottlenecked case and a pointed, steel-core, brass-jacketed bullet.
The 4.6×30mm cartridge was introduced in 1999. It was designed as a competitor to FN Herstal's 5.7x28mm cartridge.
Compared to conventional assault rifle cartridges one can carry more 4.6×30mm ammunition due to the lighter weight and relative small dimensions of the cartridge. Also, due to the lighter weight of the bullet, aiming in rapid fire is much easier as recoil depends much on the weight of the bullet. CRISAT testing shows that because of the smaller diameter and high projectile velocity of the round, body armor penetration is higher than that of traditional handgun projectiles.
The 4.6×30mm cartridge has been claimed to have low terminal effectiveness, especially by those who disagree with the "energy dump" theory of wound ballistics, such as Dr. Martin Fackler. Kinetic energy manifests itself in human tissue in temporary stretching of tissue, which most tissue except for liver and neural tissue is able to withstand with little ill effect. Slow motion videos show that the 4.6 mm bullet yaws at impact on soft tissue. This is because the center of mass of the bullet is behind the geometric center, causing the back to come forward at impact, and therefore tumbling through soft tissue, creating much greater damage, according to the "energy dump" theory.
Testing done by HKPro in 2000 indicated that the 4.6×30mm cartridge penetrated deeper in 20% ballistic gelatin and transferred slightly more energy than the 5.7×28mm cartridge fired from the FN P90. However, a more recent series of tests performed by NATO in the United Kingdom and France indicated that 5.7×28mm was the superior cartridge. The results of the NATO tests were analyzed by a group formed of experts from France, the United States, Canada, and the United Kingdom and the group's conclusion was that the 5.7×28mm was "undoubtedly" the more efficient cartridge.
Among other points, the NATO group cited superior effectiveness (27% greater) for the 5.7×28mm against unprotected targets and equal effectiveness against protected targets. It also cited less sensitivity to extreme temperatures for the 5.7×28mm and cited a greater potential risk of barrel erosion with the 4.6×30mm. In addition, the group pointed out that 5.7×28mm is close to the 5.56x45mm NATO by its design and manufacture process, allowing it to be manufactured on existing production lines. The group also pointed out that 5.7×28mm weapons are more mature than 4.6×30mm weapons, and the 5.7×28mm FN Five-seven pistol was already in production at that time, while the 4.6×30mm Heckler & Koch UCP pistol was still only an early concept. However, the German delegation and others rejected the NATO recommendation that 5.7×28mm be standardized, and as a result, the standardization process was indefinitely halted.