Car muffler, suppressor, same basic idea. I think
Michael Baine summed it up pretty good on an episode of "Shooting Gallery". "What would happen if you took the muffler off your car and put it on your gun? Your car would be too loud and your gun would be too quiet."
.22s would be the most fun and cheaper suppressor cost too but it would be good to have a suppressed larger caliber pistol by the bed for self-defense. That way I wouldn't blow out my ears while blowing away a bad guy.
That's the way to go, getting one for your 7.62 that will work on your 5.56. Getting a quick detach model and replacing the flash hider on both rifles, I'm assuming.
If I decide to get one for my pistols, I'll probably get a Silencerco Osprey for a .45. Then get adapters so I can use it on a .40 & 9mm. About $70 (I think) per adapter vs about $1000 for each suppressor.
An alternate for SBR is a bullpup rifle. Short but doesn't require tax stamp.