I have run a couple different scope with the sight towers in place setups and never had an issue, I can see it on my PM400 with the 1-6x on 1x but by the time it hits 2x the sight disappears.
I usually use SLR brakes but gave the Superlative a try when I changed out the block on my 16 inch rifle gas Matrix build. It works fine in the restrictive mode but does not allow enough gas out in by pass mode. It also runs a bit dirty in bypass mode. I would stick with the SLR for a 308 build myself. Here is the thread and another picture;
I'd like to hear the details on the ammo, wonder if it is a standard jacketed bullet or one of those expensive machined brass bullets. Whatever it is it must be good stuff.
Never heard of a Colt 308 other than the 901 MARC that converts to 5.56. Very little information, nothing on compatibility.
https://www.cdnnsports.com/colt-ar308-competition-rifle-build-kit.html#.WUwAe4UpDYU
Edit; Found a four year old thread here with more info, CDNN must be clearing these out for Colt
.http://www.thefirearmblog.com/blog/2013/01/17/colt-competition-ars/
Try asking Falkor Defense, I'm pretty sure they took over SI, they were selling both for a time.
https://www.falkordefense.com/
Oh yeah, welcome to the forum!
Back on again
http://palmettostatearmory.com/federal-308-168gr-sierra-matchking-bthp-gold-medal-ammunition-20rds-gm308m.html?trk_msg=TEDP21CEOPF4763BJMS1U2IG08&trk_contact=CCM1L42B6H11OTO9IV10FHBVDG&trk_sid=6FAJJ0SVRM5DKDJ8UAG2OAR18O&utm_source=Listrak&utm_medium=email&utm_term=http%3a%2f%2fpalmettostatearmory.com%2ffederal-308-168gr-sierra-matchking-bthp-gold-medal-ammunition-20rds-gm308m.html&utm_campaign=Daily+Deal+Email&utm_content=5%3a00+Email
If it is locking back after firing one round in the mag then the gas should be good, maybe a stronger ejector spring? Might just smooth out after a few boxes though.
Another vote for D. Wilson.
http://www.dwilsonmfg.com/store/p18/AR10_Bolt_carrier_Group.html
Again, these are DPMS platform and not AR-10 as the title suggest.