I can't speak to the McCormick but, I've installed AS FCG's in every AR I own. I removed JP FCG's from 2 of the AR's because, although I'd never had a problem with them, those screw adjustments made me nervous. The AS stuff is bascially stock FCG components with re-engineered sear geometry; no adjustments, other than the trimming you do for initial installation. The AS is definitely not "drop in". You will need jewelers' files, a stone, and some patience. However, once you've installed it, it's there forever.
The AS will not give you the absolutely perfect let-off you can get from a JP or Jewell adjustable and it will have a little bit of over-travel; but it's WAY better than stock and it absolutely will work every time.
Although Derick is off serving his country, the same guys as always are turning out the FCG's. His wife Cheryl is taking care of orders and shipping. Derick is not only the kind of guy who goes off to serve his country without hesitation. He is also a glazed-eyed, frothing-at-the-mouth fanatic when it comes to reliability. His attitude is that his shit will work every damned time. No excuses.
Luck,
SD