 The M134 bomblet, developed as the E130, or E130R1 bomblet, began development in the early 1950s.While the weapon was not yet battle-ready, or ready for mass-production, in 1960, work on the bomblet dated back to at least 1953.By 1964 the bomblet design had been improved and the smaller M139 was adapted for use with the rocket warheads utilized by the M134.