$LoopFiringSnd: doesn't work, and a few other things.

Whilst $startfiringsnd: and $endfiringsnd: work as expected, $loopfiringsnd does not and plays no sounds.

Atm I'm trying to give BP's Gattler a proper minigun spin-up and spin-down sound (As it takes a second to fire, and I want the player to hear something to indicate that this spin up is happening). However, if the player simply clicks the button, the $startfiringsnd keeps playing. Ideally you'd want $endfiringsnd to cut off $startfiringsnd and $loopfiringsnd.