I just made a purchase on this barrel from midwayusa.  Did I make the right choice?  

Here

I have one on a plinker and it works just fine.

I also have one.  Added a KX3 Flaming Pig and Sig Stabilizing brace.  Very happy with it. Shoots good, no problems, great value. Just know that with that barrel length you are very limited in ammo selection if you plan on using it for anything other than a range toy.

please elaborate on the "limited ammo selection"...
I am considering using one of these for a pistol project.

Contrary to what I've been told my whole life, size does matter, especially with the AR platform.  The .223/5.56 in military applications does its damage by tumbling (yawing) and fragmentation once it hits its intended target. The fragmentation is very dependent on the bullet velocity.  For 55 grain XM-193 the critical velocity is 2700 feet per second.  Reliable fragmentation will not always occur at speeds slower than that.   Barrel length has a direct correlation on velocity.  With a 16" barrel, 55 grain bullet will have a muzzle velocity of about 3100 fps, but that same bullet from an 11.5" barrel has a muzzle velocity of around 2850.  Drop an inch off and now a muzzle velocity of about 2725 fps from a 10.5 barrel.  Remember the 2700 fps for reliable fragmentation? You are almost at that threshold at the muzzle.  In the event you don't get any fragmentation you will basically have a through and through .22 injury.  With a 7.5" barrel you will need an expanding design round, preferably a bonded  HP, but not necessarily a varmint round because they don't penetrate deep enough.  A very recommended round for the 7.5" is the Black HIlls TSX 50 gr.  It can be expected to expand reliably to about 25 yards from your barrel.

Frangible 52gr should work fine.

Thanks for the info Capt!

2Truckus, I am by no means an expert.  I just did a lot of research about this in the last month.  If you decide to go with the KX3, I would recommend the Samson Evolution freefloat handguard.  The piggy fits very nice within, and is available not only online but also at Bass Pro.  I am very happy with mine.

Capt, what kind of gas tube and buffer set up do you have?  Building one of these up at the moment but havent gotten to the (apparently most vital) point of buffer weights and tube lengths.  Want it to be as trouble free as possible.  I did go ahead and order a YHM lopro gas block as well as a Noveske pistol length gas tube.  I know these pocket ARs can be challenging, but I'd rather not be beating my head on the bench too much if I can learn from others who have it up and running!  Thanks in advance!

I have a similar setup with this barrel.  I went with the AR Stoner barrel, CMMG pistol length gas tube, YHM clamp on gas block.  To increase reliability I went with the Spikes ST-T2 buffer, BCM bolt upgrade and I'm using the Troy Claymore muzzle device to provide back pressure similar to the Noveske.

I just picked up one of these for a pistol build as well. Is the barrel dimpled for set screw gas blocks or will I have to drill press it?

I dont think they come dimpled for the set screws.  I installed the YHM low pro gas block and it was extremely tight but works.

Not dimpled for gas block.

I used the Phase 5 Tactical receiver extension (buffer tube) kit which included the complete standard weight buffer assembly for about $70.  For gas tube, it was a pistol length from Palmetto State, I believe.  If they don't have them, JSE surplus or Primary Arms has them.  I fired another  20 trouble free rounds today with it before being told that I couldn't shoulder the Sig Pistol Brace as it would be a violation of the NFA at my local (Shoot Straight) range.  I told him if it was against their rules, that's fine, its their range, but it is NOT a violation of NFA to fire it that way.  I then packed up and went home.  Anyway with American Eagle .223 standing, bent over, supporting my arm on the counter at the range, all 20 rounds at 20 yards could be covered by a dollar bill folded in half.  Gun is more accurate than me.

100 rounds 100% so far.  Hope this helps.

Thanks for the info!  Sorry your range has some issues it needs to work out.  Are you using a regular buffer or a heavy buffer in it?

Currently using a regular buffer, but I do have a heavy buffer that I was going to swap out yesterday at the range just to see if I could notice any differences but didn't get the chance.  I'm not looking to fix anything that isn't broken, but I keep a heavy buffer in my range bag to help diagnose any AR problems.  Ejected shells launch to about 2 O'clock, and again, flawless.  I am happy with the Stoner barrel.

Went to the range over the weekend and tested out my pistol with the AR Stoner Barrel.  Ran 30 Rounds of Winchester 55grain out of an Lancer Mag and ran flawlessly!  No hiccups or malfunctions whatsoever.  I am very happy and have no complaints on this barrel.