I don't think there are any aftermarket muzzle devices for the SOCOM yet, due to the unique construction, as in combining the gas cylinder lock with the comp. The normal M14 flash hiders, whether USGI style or aftermarket, won't work.
I have seen a custom piece done by Arizona Response Systems where the original comp/brake was removed from the gas cyl. lock and a short open ended FAL flash hider welded on, which resembles a Vortex at first glance.Made for a good looking piece. From the pictures, you couldn't tell it wasn't factory.Was posted over on the FALfiles a month or two back. Gunplumber (Mark Graham) is the smith that did it and I *think* stated he would do the work with customer supplied parts , but don't quote me on that. I've slept since then.