will need to set up the animation so that an emote enables the particles.
to do this hide the weapon after its on your wrist.
then set up an emote using this method
then open armature ->hips -> Spine -> chest -> right shoulder > right arm-> right forearm ->Right wrist -> DesertEagle
click the plus next to is active and do the another animation for the firing. which is done the same way. then set these up as 2 separate emotes on the avatar.
this is not for beginners you need to have learned some very basic animating before attempting this. but all the files are there'