The 4.6×30mm (designated as the 4,6 × 30 by the C.I.P.^[6]) cartridge is a small-caliber, high-velocity, smokeless powder, rebated, bottleneck, centerfire cartridge designed for personal defense weapons (PDW) developed by German armament manufacturer Heckler & Koch (HK) in 1999. It was designed primarily for the MP7 PDW to minimize weight and recoil, while increasing penetration of body armor. It features a pointed, steel-core, brass-jacketed bullet.

The 4.6×30mm cartridge was introduced in 1999 as a competitor to FN Herstal's 5.7×28mm cartridge.^[7] Heckler & Koch started the development of a semi-automatic handgun for their 4.6×30mm PDW cartridge, but Heckler & Koch cancelled the Universal Combat Pistol (UCP) at the prototype stage.

Compared to standard intermediate cartridges one can carry more 4.6×30mm ammunition due to the lower weight and relatively small dimensions of the cartridge. Also, due to the lower 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.

A series of tests performed by NATO in the United Kingdom and France indicated that 5.7×28mm was a superior cartridge.^[7] The results of the NATO tests were analyzed by a group 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.^[7]

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.^[7] 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.^[7] In addition, the group pointed out that 5.7×28mm is close to the 5.56×45mm NATO by its design and manufacture process, allowing it to be manufactured on existing production lines.^[7] 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.^[7] 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,^[1][7] though both cartridges would ultimately be standardized by NATO with STANAG 4509 for 5.7×28mm and STANAG 4820 for 4.6×30mm respectively.

The 4.6×30mm has 0.87 mL (13.4 grains) H₂O cartridge case capacity.

4.6×30mm maximum C.I.P. cartridge dimensions; all sizes in millimeters (mm).^[6]

Americans define the shoulder angle at alpha/2 ≈ 22 degrees. The common rifling twist rate for this cartridge is 160 mm (1 in 6.3 in), 6 grooves, Ø lands = 4.52 mm, Ø grooves = 4.65 mm, land width = 1.21 mm and the primer type is small rifle.^[2]

According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings, the 4.6×30mm can handle up to 4,000 bar (400 MPa; 58,015 psi) Pmax (the nominal maximum) piezo^{[clarification needed]} pressure. In C.I.P. regulated countries, every rifle cartridge combination has to be proofed at 125% of this maximum C.I.P. pressure to be certified for sale to consumers, referred to as "PE". This means that 4.6×30mm chambered arms in C.I.P. regulated countries are currently (2018) proof tested at 5,000 bar (500 MPa; 72,519 psi) PE piezo pressure.^[6] Despite the relatively high Pmax the bolt thrust of the 4.6×30mm is on a similar level when compared with traditional service sidearm cartridges.

The Belgian 5.7×28mm cartridge introduced in 1993 is probably the closest currently available ballistic twin of the 4.6×30mm.

The 4.6×30mm ammunition is produced by RUAG Ammotec, Fiocchi and BAE Systems.