I recently bought a new Double Star Upper from a dealer off of Gun Broker.com.  Upon assembling the kit and wanting to fire that first round through it, I went to the back yard and jacked a round through it.  To my surprise, the chamber wouldn't fully close.  I ejected that round and the next one wouldn't load up either.  Upon inspection, I could see that part of the brass from the first round was still in the chamber.  I searched around and found about 1/2" of the case lying on the ground.  After contacting J&T Distributing, I had it in the mail.
I got it back today with a letter with the following explanation:  "Roughing Reamer was left in barrel too long.  Therefore headspace was off and barrel was bad.  I replaced barrel and test fired.  Worked perfectly."  Does this explanation sound right?  He assured me over the phone that it was not the ammo and that it was excellent ammo (Remington white box UMC).
Seems to me like their QC department should have caught this kind of defect.

Shit happens.

They fixed it.

Have fun with your new rifle.

i had them build two uppers.

the first one... they forgot my order, but gave me some free stuff in return.

the 2nd was a FTF they built it for me while i was running around, they had to try twice since they put the wrong flash hider back on. but fixed.

i later went home to find that the retaining pin on my troy rail was crap. the rail uses a pin, someone had lost it or somthing, because what was in mine was a small aluminum ball bearing.

i called them and troy, they said i could send it in but i figured that would take too long sinc ei could fix it myself.

i tried to get the replacement part from troy, but they misunderstood me and sent me a rail clamp for a BUIS... the wrong part.

being all i needed was a small pin spring loaded to fit through two holes i machined one out of a brass rod.

so they do screw up. and help to fix but i dont think they try real hard
-p.s i was dealing directly with J&T they are located about 45min from me.

Only one double star lower at present. Quite inpressed with there work man ship. As far as a whole rifle. I cant say. Personal experance with several Ar makers and there assebled rifles. Is what drove me to learn to Buld it myself. If I am going to trust my life on it. I want to make sure I pick the best parts. And spend as much time puting them together as it take's.

I started out on my AR's about a year ago, and have built two of them.  The first one was on an RRA lower with a 20" varmint kit from m-aparts.com (LMT upper and Wilson barrel).  The second was on a DoubleStar lower with a 16" lightweight kit from model1sales.com (unknown upper mfg with ER Shaw barrel).  The second one didn't go together as easily or as well as the first.  Roll pins didn't install as easily/cleanly, and I even had to file down the sides of the trigger to get it to go down into the lower receiver.  I don't know if the fitting differences I experienced were because of the uppers, lowers, lower parts kits, or a combination of them all, but I am much happier with the first one I built vs. the second one.  That is not to say I am not happy with the 2nd one, but just that I was more pleased with the results of the first one.

I think for my next one (if I can ever get around to it), I'm going to try a billet lower from either SunDevil or POF and am undecided on my next upper.

My .02....Mike W.