FN 303 The FN 303 is a semi - automatic less - lethal riot gun designed and manufactured by Fabrique Nationale de Herstal . The FN 303 ' s projectiles have been specifically designed to break up on impact , reducing risks of penetrating injuries . Typical operating scenarios include domestic violence intervention , marking violent suspects and building surveillance . Overview . The FN 303 uses compressed air to fire projectile s from a 15 - round drum magazine . It is designed to incapacitate the target through blunt trauma without causing critical injuries , and is most widely used for riot control and other kinds of combat where lethal weapons should be avoided . The 303 can be fired from the shoulder using adjustable iron sight s , or it can be mounted in an under - barrel configuration on most assault rifle s when its stock assembly is removed ( in this configuration , it is designated " M303 " ) . It also comes with a top - mounted Picatinny rail that can fit most commercial weapon accessories , such as telescopic sight s , laser sight s and tactical light s . FN markets its own set of accessories for the launcher , including tactical vests , slings , carrying bags , and gas compressors . It is accurate at distances up to . Development history . The FN 303 is based on a proof of concept project originated by the Monterey Bay Corporation and designated the XM303 by that company . The development team consisted of designers and researchers from two paintball related design and manufacturing firms — Airgun Designs and Gun F / X Tactical Development , a division of Pro - Team Products . The proof of concept prototype was named the UBTPS , Under Barrel Tactical Paintball System . The design could be attached to an M16 rifle and was conceived as a less - than - lethal weapon system coupled with a lethal weapon system , providing a wide range of response capabilities that were immediately available . A stand - alone version was also developed . The UBTPS also featured a rotating barrel magazine , allowing for a wide range of different projectiles to be available and selectable without the need to change magazines . Monterey Bay Corporation and specifically Gun F / X Tactical Development also developed the bismuth - weighted projectile to provide the necessary mass , allowing the UTPBS to achieve the engagement range requirements . Ammunition . The FN 303 fires a spherical , fin - stabilized projectile . According to FN , the fin - stabilized design provides greater accuracy than a standard paintball round . The forward half of the sphere is a non - toxic granulated bismuth shell designed to fragment on impact to prevent penetration damage . The rear half of the sphere contains one of several color - coded liquid payloads : Safety . In 2004 in Boston , a FN 303 round killed Victoria Snelgrove when it struck her in the eye , causing her to bleed out before medical assistance arrived . Subsequent tests by Boston Police indicated that the 303 ' s accuracy " decreased significantly " after about three hundred firings . This is circumstantially corroborated by testimony of the officer who fired the weapon , stating that he was aiming at a rioter throwing bottles and did not even know that a bystander had been hit . A fifteen million dollar wrongful death lawsuit against the City of Boston and FN Herstal was settled in July 2006 . In 2007 the Boston Police destroyed their remaining FN303s , stating they were more powerful and lethal than had been anticipated . During violent protests in front of the ARCELOR [ former ARBED ] building in Luxembourg city on May 11 , 2009 , the weapon was used for the first time by Luxembourg police forces . An RTL cameraman was hit in the hand , breaking one finger .