I have turned into a big fan of AR pistols. lots of fun, and easy to build, tweak and modify.
I especially like them in pistol calibers. Rifle calibers out of such short barrels aren't the optimal performance rigs and they're LOUD.
Remember, you're firing a rifle projectile with powders that are designed to burn fully in an 18" barrel. and in a pistol build. you got 7" to 12" to play with.
Lots of un burnt powders coming out the muzzle. I can deal with the loudness of a .223 in a 7.5" barrel, but its the concussion that you get being that close to the business end that really rattles you after a while..
I prefer regular pistol calibers like 9mm, and 45 honestly, but I LOVE my suppressed 300 blackout with an 8" barrel. that thing ONLY gets dedicated subsonic loads and is a dream to shoot. and quiet as a .22lr.
Two of my recent, personal builds.
My 300 Blackout. Subsonic ammo only
And the 9mm SBR and integrally suppressed. 3.5" barrel. Subsonic ammo only.
You can only use a regular stock if you pay the stamp to own an SBR.
If not, you have to use a tube, or one of the new modern "braces" like on my 300. and yes, I am a licensed manufacturer and SOT2.