Looking into buying a new AR. Can't decide between .300 blackout AAC or 223/556. Any suggestions ?

223/556, ammo is cheap and easier to come by.

What are you using it for?

Hogs/ wife to shoot deer with.

For a hunting rifle platform, I'd go 300 black or 6.8....if for more recreational shooting, I'd go 556

How much does a good 300 blackout setup run? What brand and all would you recommend?

300 blackout works great for this. 223 will do it too but I personally prefer a 30 caliber bullet on game versus a 22cal. Something to look into too is 6.5 grendel, it kind of bridges the gap between 223 velocity and 300blk mass. It uses .264cal bullets and pushes them about 2500-2600 fps. Just another option. You really can't go wrong with any of the 3.

Doesnt cost any more than a similar 5.56 setup. Radical firearms or hardened arms complete rifle should run you $550-$600. i.e. Radical firearms complete rifle http://www.radicalfirearms.com/product-p/rfrifle.v2.16fgs-mil300.htm
The 300 and the 5.56 are the same price. You could also get an ar pistol in a 10.5 barrel config in 300blk and have a nice compact rig.
I can testify for both companies. I have had both and they were good quality and shot good.

6.8 is the way to go hands down. I will reload 95 gr ttsx near 3000 fps this fall and from what I have seen it does a really good job. Personally I wouldn't buy an AR either but rather build it from the ground up. Look at ARP barrels for 6.8.

X2 on the Hardend Arms! I can build a Anderson Arms lower and a Hardend Arms upper, bolt carrier and charging handle for about 650 and it will look and ACT like a 900-1000 dollars AR-15!

I vote you build your own instead of buying...you come out cheaper in the end, regardless of what caliber you choose. Seriously, you'll end up buying a stock rifle and then want a new stock, rail, comp/brake/flash hider, grip, trigger guard, trigger, etc. You'll take a $550 AR-type stock rifle and end up dropping $700 on it in accessories over time and have parts leftover. Or build your own for around $800-$900 that'll be exactly what you want and out-shoot most rifles costing much more.

I built my latest one (bought my first one and built 3 now) last year using an Anderson upper and lower, Anderson BCG, Green Mountain 1:7 fluted barrel, slim Midwest Industries rail, Magpul stock, a Primary Arms 4-14x44 FFP Mil-dot scope and mount, and all the other misc parts for barely over $900 and the thing shoots better than some of these $1500+ RRAs, Larues, Daniel Defense, etc (handloads mind you). Watch for sales (Memorial Day is a great sale time) as it'll help a lot.

The caliber depends on your ranges to engage targets in my opinion. If you can keep it under 100 yards for your wife, then I'd go 223/556 for cost of ammo for other recreational activities with the gun. If you're thinking up to 200 then a 300 BLK would serve you well as hit harder, and the 6.8 SPC extending a little further to around 300 (sure people claim longer, just talking about good energy retention here).

Personally, I'd build a 223/556 first (that'll be alright to shoot some deer up close with and do other things with and save ammo costs), then save up for and get a dedicated 6.8 SPC upper and BCG to swap in later down the road. It'd be the best of both worlds, although trust me: I've tried using multiple uppers/calibers on one lower and I just end up wanting to buy another lower and have dedicated rifles hahaha

Good luck man and let us know what you decide

Anyone have a guide they would recommend for building a .300 blackout?

I'd just watch some YouTube videos if you feel uneasy about doing it yourself. Who knows, they likely have some folks with 300 BLK builds on there as well. Worth a shot at least.

If you want great quality with a budget in mind, definitely use an Anderson upper and lower. Best $90 you'll ever spend on a build foundation. Wish I knew more about 300 BLK barrels and what folks like, but I do not so I'll defer that to others

Here is your guide:

1. Buy a stripped lower locally for about $50.

2. Buy a lower parts kit, BCG, and charging handle from Palmetto State Armory.

3. Buy a Radical Arms Upper that is already built.

Assemble. Thousands of youtube videos.

Determine optics.

Check out midway USA, brownells, and opticplanet for AR building videos. It is pretty simple to do and fun at that. You don't know what you are getting when buying used and you can save a bunch of money putting the gun together yourself. If you go the build route I (As well as others who have built their own) can suggest quality or budget parts.

Nothing wrong buying a complete radical firearms rifle for $550. Has everything you need, sometimes they run specials and you get em for $499. Wont really save much money building one. Has a good free float rail and quality components from the factory. Plus if you ever sell it, most people are quicker to buy a factory rifle than a home build. Dont get me wrong, i enjoy building them but for your first, a radical firearms or hardened arms would serve you very well and is built very well and really close in price to building your own.

Just assembled my first AR, a 5.56, all PSA parts. If I was to purchase a 300 blk upper from Hardened or Radical, would my current BCG work in that upper? Any other info I need to know?

The only difference between 5.56 and 300 blk is the barrel and the ammunition. Do not confuse the two if you have both flavors of ammo laying around.

you can also neck down and trim a 5.56 case to reload 300

5.56 and 300blk use the exact same bcg.