The original hand guard is a proprietary setup from Q. I believe it's called Q-sert. They claim it has some crazy shear strength compared to MLOK, but so far I haven't been impressed with it's practicality. Your only option for accessories is from Q directly. I've got the two picatinny rail sections that came with the rifle, and I've ordered one of their sling swivels. The Q rail sections are only available in one length. Great for a bipod, but too short for a RRS dovetail mount (only two of the three screws can engage).
The Q-sert sling mount is garbage. It assumes that there's space inside the hand guard for the end of the swivel. I've got a pre-ordered rifle with a factory installed 24" Proof research barrel that has a greater OD than any of their steel barrel options. If I put Q's sling mount on the rail and then try to attach a sling, the QD swivel on my sling can't engage without pressing directly against the barrel. I'm currently using a Magpul product that attaches to the top rail and has a sling mount angled down at 45 degrees.
Does anyone make any accessories aftermarket for these rifles, or are we stuck with the factory accessories that use a proprietary mounting system?
Are there really not enough of these out to market to really support that yet?
Seems like someone could jump in and make a few accessories like sling mounts and longer rails pretty easy, or is the fear of litigation to strong of a deterrent for most. Assuming that there is some sort of patent/copyright deal with his proprietary mounting holes.