In June 1953 work on High-Velocity Small-Caliber cartridges at Aberdeen Proving Ground was upgraded from its previous low priority status to that of an assigned project.
With the CAL 22 CARBINE results in hand the next logical step was the design of a bullet and cartridge having acceptable characteristics for full size rifle use. Prototype ammunition was prepared using modified components of existing commercial and military ammunition. Test weapons were fabricated and some preliminary testing was conducted. The results indicated that the experiment was sufficiently promising to justify further pursuit. The project was assigned to William C. Davis, Chief Engineer Development and Proof Services.
The first step was the design of an appropriate bullet. Essentially, it was a 68 grain GM jacketed lead core 22 caliber homologue of the cal 30 M1 ball. (I believe Davis was the first to use the term