Had to change skin names in order to function with Apply Skin to Attachments check box in the Customize Item menu.

Updated to 1035.1! Includes black skins for the rifles and the included XM8 magazine. Disregard all of the other changes. I thought I messed up my tags for the magazine's skins, but I apparently had that matching skins checkbox checked on the XM8, so no color options showed up for any attachment.