The .224 Boz cartridge was developed in the late 1990s, designed as a candidate replacement cartridge for adoption as the standardized NATO ("STANAG") Personal defense weapon PDW round, originally solicited to replace the longstanding NATO standard (STANAG) 9×19mm Parabellum.

It was going to be the British entry, to be evaluated alongside the Belgian FN 5.7×28mm and the German HK 4.6×30mm armor-piercing cartridges.

The solicitation would also seek to find, test and standardize a PDW cartridge capable of, at the minimum, defeating the Collaborative Research Into Small Arms Technology (CRISAT) body armour of the time.

Original trials were successful, with this round firing a 50 gr (3.2 g) projectile chronographed at over 2,500 ft/s (760 m/s).

[3] During development a version based upon the 9×19 Parabellum case was also evaluated, which carried the significant advantage of being able to be utilized in pre-existing NATO standard 9×19 Parabellum caliber firearms by means of a relatively cheap barrel and caliber swap.