Colt is probably the most reliable AR15 on the market. The down side is they don't have as many options in caliber and style. You can get 5.56 and maybe 7.62.
Not sure why you are set on the .308 and subsonic rounds. Its kind of counter productive. 308 would be in the AR10 platform and IMO the reliability is just not there from any brand.
Rock River Arms is a great bang for the buck AR. They have a great lower that has a stage 2 trigger. One of the best on the market. They have several styles from compact carbine to heavy barrel target type guns. Several calibers 5.56, 6.8, 7.62, ect all in the AR15 platform. You can get one of RRA lowers with the stage 2 triggers and go to like AR Performance, Bison, ect and get different uppers. Those will all do around 3/4" groups @ 100yds.
I do a lot of hog hunting with ARs. IMO the 6.8mm is perfect. You can shoot from and 85-120gr bullet. Its great for 0-300yds which is all you will be shooting most of the time. Its a great mixture of knock down, low recoil, and reliability.
I have two ARs. One is a Rock River Arms lower with and AR Performance upper in 6.8mm. The other is a Rock River Arms Coyote Carbine in 5.56. I have an adapter so that I can move my suppressor back and forth. For the moment I have a Leupold scope on my 6.8 because I deer hunt with it and I have my night vision scope on the 5.56.
My advice is to not get hung up on the subsonic rounds and all that 300 Blk out stuff. The reality is subsonic rounds are quiet because they are slow. Less knock down. A suppressor will also slow the bullet down. On top of an already slow round. When you shoot hogs they will run not matter how quiet you think you are... once they have been shot at. Get some thing with good knock down both short and med range.
