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37mm rubber bullets in the early years

The 1960’s saw the introduction of 37mm rubber bullets as a governmental response to the social and political upheaval in both Europe and the United States. Within a democracy, deadly force was not an acceptable option in containing or disbursing crowds. This was evident from the fallout of the Kent State fatal shooting of Vietnam War protestors by the Ohio National Guard. In the years that followed, the United States Army began to develop less lethal rubber bullets to avoid casualties when dispersing crowds.

Early rubber bullets were 37mm caliber munitions. 37mm launchers were developed to deliver tear gas munitions for area dispersal, but later adapted to deliver rubber bullets for crowd and riot control. Because these rounds lacked energy absorption, users would fire rounds against the ground causing a bounce that were intended to hit targets in the leg or lower body in order to reduce injury. 37mm launchers were smoothbore barrelled and not designed for direct fire. The resulting lack of spin meant short range and reduced accuracy.

The move to 40mm rubber bullets

The increase of military intervention and subsequent peacekeeping operations in the 1990s and early 2000s led to increased requirements for less lethal ammunition due to the political costs associated with using lethal force against the civilian population. US and NATO forces were equipped with rifle-barrelled 40mm grenade launchers that greatly increased projectile range and accuracy.

This improved ballistic performance created a new market for 40mm rubber bullets for use by those military forces. Beginning with US SWAT, police forces began to convert in the early 2000’s. This gave law enforcement and the military increased capability reducing risk with great accuracy and range. Although 40mm rounds were an improvement over 37mm, the material nature of those rounds being plastic, foam and rubber still had high risk of trauma injury due to lack of energy absorption.

SDI’s development of its 40mm Blunt Impact Projectile (BIP) raised the bar on less lethal ammunition. Although some manufacturers produce rounds that cushion to some degree, the SDI BIP with its patented collapsible head mushrooms on impact, spreading kinetic energy and the pain across a greater surface area, while significantly reducing the risk of trauma injury. The internal energy absorption system based on the initial cushioning of the gel head, creates a secondary double tap via an energy expander in a second wave of impact, inflicting more pain.

The evolution of 37mm rubber bullets from the 1960’s to the SDI Blunt Impact Projectile of the 21st century is a similar evolution to automobiles without seatbelts, to seatbelts and finally to airbags. The SDI BIP gives governments more flexibility in pain compliance and reduces risk in a world dominated by internet and social media, where excessive use of force is instantaneously broadcasted around the world, undermining the legitimacy of political authority.