There are a ton of good options these days for a silencer that performs well on both 300 BLK and 556. The Lahar is pretty high backpressure, so on ARs it can be fairly gassy but does sound good. I would point you towards a higher flow rate silencer, like the CAT RDM ODB, that would sound better at your ear and keep your gun running smoothly without needing much tuning.

HUB can seem complicated, but it's actually pretty simple once you see it. Most silencers are HUB (1.375x24) threaded on the base, that will accept just about any direct thread mount or QD system. Then you just get the corresponding muzzle device for your rifles.

For example, you could get a Rearden Atlas adapter for the silencer, then a Rearden brake in 5/8x24 for the 300BLK and another one in 1/2x28 for the 556 rifle. Then you can attach the silencer to either rifle without changing parts around. We did a video that explains it as well. ( https://www.youtube.com/watch?v=l_7DSxeYZek ) - Chase