I did up a 300bo setup a few years back that has been living in a Sentinel Concepts Revelation II.
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the gun is a 8.5" 300 blackout "pistol" with a law folder and a silencerco omega 9k, making it about the same length as a 10.5" with a flashhider.
Nice to have, its always just sitting ready to go, gets new batteries on my birthday and only gets shot a few times a year really, usually when someone wants to try out a 300bo.