Hey everybody.
I am getting ready to start my first AR Pistol build. I just got a new stripped Anderson lower in yesterday from Fat Boy Tactical. That's where I am starting and looking for any advice or suggestions on barrels, hand guards, buffer tubes, etc....
Thanks in advance.

What is your goal?

barrel length
quadrails or not
etc

I'm thinking 10.5 inch barrel, not sure if I want quadrails or just a smooth handguard yet.  Muzzle break and LPK.

caliber?

I built my .22lr with a 10.5" barrel with the Diamondhead VRS-X 10.25" handguard. For kicks I used a Fortis Red SS comp.  I added the Sig Brace and a Blackdog 50rd drum mag and the pistol is now one of my favorite range toys.

I'd like to build a lightweight 5.56 AR pistol with the Sig brace for a home defense gun.  Loaded up with Hornady TAP it would have plenty of stopping ability but without the danger of over penetration that comes with high velocity handguns like the 9mm or shotguns with buckshot.  A light/laser added on would make it about perfect.

i was reading about a guy shooting TAP through a 7.5" ar at 50 yards and he was punching holes through level III armor.

TAP is considered a barrier penetrating round, not good in a house. It will zing right though several walls, great round when it hits intended target.

There are several different version of the TAPS ammo, some designed to be better at penetrating barriers and some designed to fragment easier and some in between.  While you couldn't get ten gun folks in a room to agree on anything, I've seen enough "experts" recommend 55 grain .223 Hornady TAPS as the best home defense ammo and penetration tests to base my decisions on that.

I would very much like to see a test done with the various popular handgun and AR caliber/cartridge choices done in a real house or simulated.  Putting a bunch of Sheetrock a couple inches apart is a start but we need a full scale test with more than just one FMJ as the AR sample.  That would end all the guessing.

It will have an awful flash and be painfully loud.

Nothing wrong with that, it is better than a bonded bullet for indoor use, the ,Remington PSP is another indoor favorite, old school but very good. The difference in the TAP for "LE" and the others is the powder, less flash for LE, or so I have been told, any kind of bullet beats the hell out of nothing if you need one.