In 1963, the US Army set out to purchase 85,000 AR-15 rifles as a one-time procurement to hold the infantry through until final adoption of the expected Project SPIW rifle. Where the previous Air Force purchases of the AR-15 had been simple over-the-counter transactions with Colt, the scale of this new contract prompted Robert McNamara to set up a committee to standardize the rifle requirements of all four service branches. One of the disputed items was the addition of a manual bolt closure device.

The Air Force, having tested the AR-15 for several years by this point, saw no need for such a device. The Army, however, insisted that it was necessary both as a confidence-building feature for the infantryman and because it might in some situation solve a malfunction. Today, let's discuss the sequence of events that led to the eventual January 1964 adoption of the now-familiar plunger type bolt closure device.