At one stage this development formed part of the US SAW (Squad Automatic Weapon) program, but tests with the 222 Magnum case opened to 6mm with commercial bullets, different propellants and various over-all lengths did not show sufficient progress to warrant further tests. Federal produced a limited batch of this when it was marketed commercially. Various bench rest shooters also fiddled with this idea and because some disciplines required at least .23in. bullets, the 222 Magnum case was simply opened up to 6mm and there you had it.