First off, thanks for looking

I'm about to dive into building an AR and have a few questions about J&T kits. Specifically I'd like to know about some of the parts in their EM4 kit:

They advertise Colt FCG parts, so I'd like to confirm this with you guys.

-Do they use a Colt bolt and carrier?

-What kind of buffer do they use? Is it a Colt "H" CAR buffer?

-Dual heatshields on the M4 handguards?

-Any headspace issues?

-Any QC issues like canted front sights or gas tubes? Any other problems with QC?

-How do you like the Shaw barrel? What kind of brake do they use?

-Anything else I should know about before I jump?

Thanks in advance for your expertise. The product descriptions of these kits seem almost too good to be true-and for that reason I'm a little weary. I'm hoping you can make me a believer

I purchased the assembled A2 upper + the kit less the reciever. Everything as advertised. Colt trigger etc. Be careful about the postban flash hider PERMANENTLY attached - if you want to free float handguard later on - you'll be SOL (at least for a small charge to have it removed). Great kit, quality materials. I was very happy with my purchase.

Takes about 25 minutes to put the thing together. J&T is a good company, I'll buy my next one from them - M4 lightwight :)

Not for sure on some of the answers but, I got a 16" CAR kit from them in May and have had no problems with it at all!!!

No QC problems with my kit, unless you consider that they sent me a collapsible CAR stock instead of a pinned, non-collapsible CAR stock.  This problem was taken care of promptly, though.  

There were also a few extra springs and detents in the kit, which could always come in handy!

The only other problem I had was the time it took to receive my kit.  It took a few weeks for my kit to arrive, but at the time, there was a big demand for the kit I ordered, therefore it took longer than normal.  There was also a problem with the finish that was applied to the upper receiver and barrel.  But I was patient, as I would rather have it done right the first time, than to have to send it back after I received it, only to find a problem with it and have to send it back to be refinished again.

FWIW, I will be ordering another kit from them again.  I have a MEGA lower that I am needing to build on, I just need to decide which configuration that I am going to go with.

Thanks for your help guys. So the bolt and buffer are Colt then?

Judging from the kit I built a couple of months ago:
Bolt and carrier are not Colt but are as good as anyone's. The fire control parts are Colt, or at least look like it, and they are the best of any kit parts I've ever seen.
Shaw barrel has a great internal finish. Glass smooth and free from any tool marks (mine is non chrome lined).
Finish on everything is excellent.
If you order M4 you'll get the M4 handguard, and it's top quality.
Not an H buffer.
Super quality everything.
Nothing out of order and nothing missing.
Best kit out there, for my money.

Excellent. Thanks for the info [:)]

My J&T kit has been great.  I agree completely with what has been said above as for the quality of the parts.  I had the kit 2 days after ordering it online.  

The only issue I have is that the front sight is canted.  My rear sight has to be adjusted almost all the way to the left to zero it.  It doesn't bother me too much.  Eventually I'll order an upper receiver block and fix it myself.  

The lower parts are much better than what I've seen from Model 1.  I would definitely go with J&T again.
Scott

Bought an M4 kit from them back in April.

Colt FC parts for sure.
Bolt carrier and bolt are not colt but as mentioned above are definately quality.
M4 HGs are colt and are very good, although I think I am going to dump them in favor of something with a rail on it.
Buffer is not colt, but again is quality.
Fake A2 flash hider thing (tac brake) on 16" barrel.  Works good for reducing recoil (there isn't much at all on mine with the tac brake) but is noticably louder, not mini-Y comp loud, just louder.
I got the a chrome lined barrel from them with the kit.  It was extra, but worth it.  I think you can actually get that option direct from their webpage now when you order.  I had to call and request it when I purchased.
A3 with detachable carry handle - good sights.  The damn thing was pretty much sighted in when I bought it, which was kick ass.
Locked open M4 telestock - Locks into shoulder well when shooting, a little bit of play but other than that a solid feel.  Held open with two roll pins; I don't know if its actually weleded too.  
Put it on a DPMS lower, colors matched perfectly.
Has liked all AR mags I have fed it including USGI and Brit mags.
I've only shot Federal XM193 through it so I can't say how it might handle something like Russian ammo (wolf for instance) or other cheap ammo.

Took me about 45 min to put together with interruptions.

One little Hint , If you get the J & T kit you'll save yourself the cost of a trigger Job or a better trigger later because the "Colt" trigger that comes with the J & T kits is one sweet trigger.

JT Kits run great with Wolf; it's all my friends and I use on our 16" carbines.

Though my FCG is definitely Colt, it means nothing to me.

I'm curious mainly because the chances are good that there won't be an issue with soft FCG parts if they are Colt. I've had lot's of problems with generic replacement parts in the past in my non-Colt ARs.

my buddy bought an 20inch A2 upper from them and it has gas problems.  he can't even get halfway though a mag.

i'm sure j&t will fix it when he sends it back.
you listening Simonh?