Gary Reeder
I wouldn't put much value in the 4.6 X 30 (18 caliber).
Monday, January 06, 2020, 17:12

NATO did a bunch of testing and found it inefficient and barrel eroding..here are their tests...

A series of tests performed by NATO in the United Kingdom and France indicated that 5.7×28mm was a superior cartridge.[8] 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.[8]

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.[8] 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.[8] 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.[8] 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.[8] 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][8]