My Form 4s finally came in on my two suppressors: My titanium .223 suppressor from STW and my 9mm suppressed upper from Clyde at Coastal Gun.
Only had time to break in the Coastal Gun upper. Long story short, it's awesome. I had heard good things about Clyde's product, and they were all true.
The upper is built completely around the Colt system and you get a Colt mag block and bolt with the upper. It's a flat top (A3) design and I put a red dot on it.
There was no play, at all, between the upper and my SP1 lower. I have 3 Colt mags and 4 modified UZI mags (from Clyde). All ran great, with no mishaps. I had a whole section of my local range to myself and used no ear protection (after 5 test rounds). The guys behind the glass were drooling and said afterwards that they heard nothing but the thud of the lead hitting the back of the range. Exactly what I heard (and did not hear).
No misfeeds and no noise. Simply more fun than should be allowed. The free floating hand guard protected me from heat and the entire weapon was suprizingly steady.
I used a Colt 9mm buffer in my collapsable stock and a Hogue grip I picked up from Bushmaster. I'll post pics later and give a range report on the STW can as well.
Check out Clyde's stuff over on the Bowers's Board at [URL]subguns.com[/URL]. Just go to the NFA message board and scroll down till you see him. He has pics.