This issue is a serious officer safety issues for those personnel carrying the H&K USP .45.
Department personnel who are carrying the Heckler and Koch USP .45 should take note of
problems recently identified while using the Surefire DG-19 grip switch assembly for their
weapon mounted light system.
The older version of the DG-19 switch has the potential of coming into contact with the
magazine release lever. If the grip switch comes into contact with the magazine release lever
while firing the pistol, it will cause the magazine to be released from the gun. This does not
occur unless the gun is being fired.
See PDF for more info.

http://lhs22.org/Warning.pdf