I ordered a Switchblock directly from Noveske today for my 5.56 18" middy, along with one of the AAC 308 Brakeout flash suppressors they had in stock. I'll have to swap out my MOE forearm for FF rail to use the switchblock though. They don't make an actual 18" mid-length switchblock, but they were going to custom make one for me at the normal cost, less their military discount. Their normal 18" system is something called an Intermediate length, it's a tad shorter than a midlength. They said that a 308 version is in the works.
I didn't even know they offered a mil discount, the gal on the phone told me they would give it to me when I gave them my .mil email address. Great company to deal with.
I'll give a range report when I get my can in. Should be here by the time I get back from vacation.