I have a BC 1.0 for my BCM middy. I've shot my friend's Colt 6920 with the PWS FSC 5.56, but not in a side-by-side.
At first, I thought the BC wasn't that much louder than an A2. But if you are to either side of the gun, it's noticeably louder. I don't think it's as loud as the PWS, but that's subjective.