I saw a couple people shooting subsonic .300 at a PSCL match over the weekend; it was very quiet with a silencer. One guy on my squad was badly undergassed though; he had to manually cycle the bolt multiple times.

I kinda wonder how well subsonic .300 AAC with a silencer would perform at night; I wonder if the silencer would eat enough of the very reduced gas to not create a photonic barrier. (I would need enough money for a new barrel, a silencer, and nods to be able to test this though.)