I should preface this by saying that I clearly have the Variant  strain Of Black Rifle Disease and I have a special weakness for the 7.62x39..  So here I have my 3rd AR Pistol , and it is also my third AR (2 carbines and this pistol)
I was looking around for a 8inch 7.62by 39 barrel and Bolt and Stumbled across Apha Shooting sports complete Upper with 8 inch barrel , There 9 inch Rail ( an Homage to Noveske perhaps?)   their flash can and a bolt.  I did  a search , the company appeared to review well  and I decided to buy it.  On sale for $479 it arrived at my door , shipping from California to New Hampshire for $501. Ordered on a Friday afternoon it arrived Wednesday morning.  (With naming names there are companies that should take note)
I didn't know what to expect frankly and was VERY pleasantly surprised. Fit and finish is excellent  and on first glance it far exceeds my expectations. (so Much so that I feel a little guilty about it sitting on the Budget Lower I built for it to  sit on.) No gaps no machine marks Uniform Anodizing.  I would have to say that I would  place on the level of YHM and S&W ARs I own and will look closely at the product line for my next build. That is as far as I can go with the review as it is Thursday morning and  won't be able to shoot it until Friday.
My other pleasant surprise is the SBX brace. I live here in NH on the Southwestern edge of the sate, but I had a friend  going over to a training at Sig and I asked him when he was in the pro shop to grab me a brace. I have the first generation on my other two pistols  but he brought me the SBX. What pleasant surprise Sturdy ,rests easily against your shoulder and noticeably lighter. It's just my opinion but if you were hesitating about the SBX or were choosing between the two I would go SBX
here she is.

Please forgive my photography it does not do it Justice.

Anyone making decent mags for them yet?

ASC does . What type of rail is it ?

As I said I have a couple of YHM Carbines that run the 10 or so AS mags I have without flaw (Some 7, 30 round 2 10 round and a 5 round so I can hunt..While I have shot this one yet the YHM have been flawless in their performance .

That is Alpha Shooting Sports rail mark  "Made in the USA"