Joining 2 Animation SMDs

I have 2 animation SMDs here, one for the gun, and one for the hands.
How can i join them without messing the bones? I dont want to reanimate them. This is getting me into nerves, i really want to solve that.

Try using addlayer.

Create a sequence for both, mark one as hidden and use addlayer for the other one.

Well, tried that, but it doesnt play the other anim.

Lets say i have used addlayer for the hands, only the hands play, not the gun, and vice-versa.