Have you added the layer in the layer order in project settings (see images from [SOLVED] Gun Clip Tutorial not working for me - #3 by yaustar)
Also, look at the render layers used by the weapon where that render layer is in the layer orders
Have you added the layer in the layer order in project settings (see images from [SOLVED] Gun Clip Tutorial not working for me - #3 by yaustar)
Also, look at the render layers used by the weapon where that render layer is in the layer orders