There seems to be a bit of confusion as to what is going on with this.
Sometimes it's difficult to remember that copyright and trademark, while they are both intellectual property, refer to different things. According to the US Copyright Office FAQ, copyright "protects original works of authorship including literary, dramatic, musical, and artistic works such as poetry, novels, movies, songs, computer software and architecture. Copyright does not protect facts, ideas, systems, or methods of operation, although it may protect the way these things are expressed."
While copyright covers expressions of ideas, trademark covers logos and brand names. The US Patent and Trademark Office says that "A trademark includes any word, name, symbol, or device, or any combination, used, or intended to be used, in commerce to identify and distinguish the goods of one manufacturer or seller from goods manufactured or sold by others, and to indicate the source of the goods. In short, a trademark is a brand name."
All these HK suits are for Trademark Infringement. Since BT and Tippmann aren't putting the
on any of their markers I don't think they really have a case. Patent infringement? That might make more sense but still... An air gun isn't the same as a real gun.