I built a low-budget pistol, because why not?  Components included:

Bushmaster Stripped Lower - $50
RRA LPK - $62
Andro Corp complete 7.5" 1:7 upper - $360
POS comm carbine tube, buffer, and spring - $22
Thordson tube cover and saddle - $67
POS Chinese red dot sight - ($30)

Total ~$600


Upper ran fine with a standard 3oz carbine buffer.  No signs of questionable function, with both timed and rapid fire.  Ejections were consistent at 2 o'clock.  I did notice some brass flake residue inside the action after the first few rounds.  The chamber was a little rough and left slight rings on the ejected cases - it looked like the reaming tool used by the barrel manufacturer had some nicks in the cutting blade, leaving slight elevated rings in the chamber.  I recently read a post discussing this very thing on a new Radical Firearms pistol - perhaps barrels sourced from the same place?  This did not affect function, but a slight ring of brass residue was visible in the chamber - it's pretty minor, I figure shooting a few hundred steel cases should smooth out any irregularities.
I expected a huge muzzle blast out of the bitty thing, but neglected to bring it back out at night to see how outrageous it is - next time.
The weak links in the pistol were all related to POS Chinese items.  The buffer tube loosened up twice, allowing a little wiggling of the saddle.  It wasn't noticeable while shooting, and was still limited by the thread groove and buffer retainer pin to only a couple of degrees.  I re-secured it both times with a quick shot with hammer and punch on the locking ring.  The POS red dot sight - which I didn't buy for the build but had laying around in my safe, and don't remember where I bought it or for how much, but can be had under a slew of name brands on Amazon or Ebay - lasted exactly 7 rounds, then the dot moved to the lower left of the picture.  One more round and it was gone.  I pulled off the sight, and the whole front lens assembly had come loose and twisted inside the housing.  In the can with it, so my final 18 rounds were eyeballed just by centering the target in the red dot sight window, which worked surprisingly well.  All in all, not bad - I just stuck a holographic sight on it - can't wait to run it some more.

Edit: almost forgot - the 7.5" barrel generates a bit of recoil - if you try to snug up too tight into the saddle, the charging handle smacks you in the nose.  Keeps things legal, I guess.

btt - w/ pic

good job and not a whole lot of $

Looks good! I am thinking of trying one of their uppers as well. Any regrets with the 7.5?

Only that it's not 6"  :)  It's running fine so far, and I wanted to go as short as possible.  It might benefit from a heavier buffer - not sure.  I typically shoot 223-pressure rounds - 5.56 might be a little rougher.  I might try modifying the buffer weights to slow it down a tad and see what happens.  The barrel isn't the greatest, as evidenced by the rough chamber, but considering it was a sub-$600 build made for short-range blasting, it's fine.  I found a hundred rounds of 62gr Silver Bear that I had laying around - planning on shooting it up this weekend, and expect that the zinc/steel cases to help smooth out the chamber irregularities.

Well, I took the pistol out this weekend again and ran about 80 rounds of Silver Bear through it.  The steel cases did seem to smooth out the machine marks a bit as I hoped.  I also put on a cheapo holographic site ($22 - ebay), which worked quite well.  Pistol was surprisingly accurate - I put 20 rounds all inside a 2" circle at about 60 feet offhand, which is quite acceptable.  I did notice that my cases are ejecting at about 4:00, and I'm pretty sure every case bounces off of the shell deflector (finish is wearing off the deflector already), so I think the pistol might benefit from a heavier buffer.  I'd like to modify the one that it in there, but I'm not sure how to get it apart since the buffer body only has one hole for the roll pin that holds the rubber plug.

Also, I was surprised at how little the muzzle flash was.  I expected a fireball the size of a pool table with a 7.5" barrel, but the flash wasn't much bigger than a baseball.  I guess 223 powder does all burn up w/in that short barrel length - wouldn't have guessed that.

The pin in the buffer can be knocked out and the rubber tip pulled straight out to expose the weights that are inside. I modified two of them by adding atomized stainless steel powder that was used to enhance stock bedding compound. Its just a matter of pouring in the powder and tapping the buffer on the work bench to settle it inside the buffer body around the weights. This gives you the option to go as heavy as you want up to the point where you cant put  any more powder in before putting the  rubber tip back in. Gives you the ability to make a custom weight buffer for your particular need. I did one for a 5.56 pistol build and one for a 45 acp carbine build.

I was kind of shocked the first time I shot my 7.5 pistol at the local indoor range. With mil spec 5.56 the flash was not too noticeable. The fun started with Federal 100 round value pack 223 from Walmart. Basketball size white flash from the pistol (a2 flash hider). I actually like shooting my pistol better without the sig brace. With the 7.5 upper the balance seems a little better too.

But HOW do you knock the pin out??????  There's only one hole in the tube - can it be knocked into the tube?  My buffer doesn't have two holes with a roll pin that sticks through both - it's a shorter roll pin with only one hole on one side of the buffer.  I'm planning on using #9 lead shot to increase the weight - I have a lot of that lying around.

I found a pressure vs barrel length chart that shows the exit pressure in a 7.5" barrel is a little under 17,000psi, vs about 7000psi for a 16" barrel, so it stands to reason that a MUCH heavier buffer is probably appropriate.

Basketball-size would STILL be way less than I expected.  A friend of mine used to have a 7" AMT automag II in 22 mag.  We used to shut off the lights on the range and fire it just to look at the fireball - it threw a plume that was at least 3' in diameter and 5' long.  With a 22 mag being that impressive, I figured a 223 with similar barrel length would be twice as big.  Evidently not.

Any other reviews?

I purchased one of these as well.  For $350 I'm not sure you will find a better deal.  Upper looks like an aero precision.  Unknown bolt and carrier, but was staked properly.  I believe they are using ballistic advantage barrels.  Fit and finish were superb.  

Best part was communication, very fast replies to my questions.  I wanted a 9in rail with the 7.5 barrel as I had a KAK flash can already to tuck under it.  Not a problem, and they didn't even charge me extra for what I'm assuming was not the normal request.

I have yet to shoot mine yet, but will do a full write up once I get some rounds down range.

JestersHK

I went with one of their Mk18 (10.5") clones for $400 with the intention of ditching the rail for another project and swapping in a standard car handgaurd.  I also wanted fixed A2 sights as well.  

I'm not sure of the make of the upper.  As someone stated, it might be Aero.  Mine does have a o forge mark and minimal research says PSA was selling some of those.  

The barrel is Ballistic Advantage.  I have two of their 5.45 barrels and like them just fine so far.  The melonite finish is nice.  I can't comment personally on the accuracy because I have not done any bench rest tests but all the reviews I've read are favorable.  

The BCG is of full auto profile and unnamed brand.  It is not chrome lined, but is staked properly and mine came with an o-ring installed.  

The only slight issue on mine is that the A2 FH is slightly overtorqued and not quite centered.  I don't have a problem with that.  It's only barely noticeable.

Mine ran fine with both m855 and wolf 55 gr., but I am using a rifle length buffer setup with my pistol.  I'm sure it would do fine with a carbine, but I haven't tested it with a lighter buffer.  

All in all I'm pleased with mine and do not regret the purchase whatsoever.    

I am suprised there isn't more feed back on these. Based on their posts in the ee, seems like they are moving a ton of them.

any one else? at 325, it is almost hard to pass up now.