The Mauser 86SR is an upgraded Mauser SP66. It features a new bolt, and a different stock which is ventilated to help dissipate heat from the barrel. The 86SR also features a detachable box magazine, a useful feature for both Law Enforcement (Change from high penetration to low penetration rounds quickly) and military (Rapid reloads). The rifle is a little longer, and a little less weight then the SP66. But the accuracy is no less and it contains more modern day parts.