All I've decided so far is that I want it to be 9mm.

Everything other than that is up for grabs.

Thoughts on an AR platform vs other choices?

Side charge vs regular charging handle?

16" rifle vs short barrel w/ a brace?

This will be a fun gun for the range / shooting steel.

Cross posted in Armory PCC sub-forum for more answers.

I shoot PCC for USPSA and like to tinker... I have several 9mm ARs, a 10.5 Colt format mag block for my registered SBR, and Glock 7.5" AR pistol for the house, and 16" for USPSA

are you a competition shooter (steel challenge, USPSA style practical)?
do you hand load 9mm?
determine which magazine format... Colt or Glock
do you need a last round bolt hold open?
make sure the barrel throat is for cartridge OAL of choice
don't overlook the cost of an optic, and most likely a better trigger for competition use

I went with a New Frontier Glock format lower and PSA 16" upper, with a NFA modular bolt.. I like an A1 stock, so buffer weight was easy to experiment with... would suggest a total buffer and bolt weight around 21oz...I don't need a side charger, or last round bolt hold open, so the price was kept down... I needed to ream the throat to accept 1.140" loads...I use a single dot Vortex SPARC II, and a DIY trigger job

the recoil is greater than a 5.56, but very limited muzzle blast...

if you have any specific questions, mine was built specifically for USPSA PCC division.. others have different intentions for their PCC

Now that you can fire a pistol with a brace off your shoulder, an AR-15 with a brace makes more sense than it used to.  In some states there are advantages - such as being abel to carry an AR-15 pistol loaded as a truck gun with your pistol permit - where the same may not be true for an AR-15 carbine.

On the other hand, if you plan to compete with you pistol caliber AR, you can't use a braced pistol in a match (under the provisional rules), so a 16" carbine would be more useful in that regard.

There is about a 3 dB reduction in noise with a 16" 9mm luger AR compared to a 10" 9mm luger AR.  That's about half again as much difference with the shorter barrel - but both are much less obnoxious than a 5" 9mm pistol, or a .223 pistol or carbine.


I prefer the Colt pattern 9mm AR.  If you convert surplus Uzi magazines the cost per magazine is under $15 (but there is no tab for the bolt hold open device).  If you shop around you can find Metalform made 32 round magazines for between $27-$30 (RRA and Brownells sell them with their stamp on the floor plate as well). The Metalform magazines use the same shape as the Uzo magazines but as an extrusion rather than a folded and tack welded piece of sheet steel, so there is room in the back for a LRBHO tab.  They are very durable and reliable magazines

The Glock pattern might make some sense if you have Glock pistols, but then again you generally use a 30-32 round magazine in an PCC, while you don't do that in a concealed carry pistol, so you're still buying new magazines.   For all practical purposes a last round bolt open device isn't an option with the Glock pattern magazine AR.

I prefer to have a last round bolt hold open device on my AR-9s.  It's nice to hear/feel the bolt lock back on an empty magazine.   The downside is that you'll break the bolt release on it if you have excessive bolt over run, so you'll want to run an extended buffer and perhaps a heavier buffer with a Colt pattern AR. If you have a mix of Uzi and Colt pattern magazines you can choose them accordingly to have or deactivate the LRBHO device based on need.

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Hand loading can add a new dimension to a 9mm AR pistol or PCC as you can use slower powders to tailor the load to the longer barrel.  Slower powders will give more velocity in the longer barrels, although it's somewhat relative as a "slow" powder for a 90 gr or 115 gr bullet is faster than a "slow powder for a 147 gr bullet.  

Using power pistol, I can launch 115 gr bullets at 1500 fps in a 16" barrel and still be a few tenths of a grain under the maximum load, and a bit over 1,600 fps is possible with a 90 gr  bullet.  Combined with 2 to 2.5 MOA accuracy, the reasonably flat trajectory (for pistol caliber) allows for point blank holds out to about 150 yards with a 125 yard zero.