Build a 9mm PCC – Quarter Circle 10 Side Charging QC5 Builder’s Kit

QC10 PCC
QC10 PCC

U.S.A.-(Ammoland.com)- If you're a big fan of AR platform Pistol Caliber Carbines (PCC's), you've likely heard of Quarter Circle 10 before.  If you're like me and have less experience with these diminutive lead-spitters, QC10 might be a bit of a new name in your mental Rolodex.  To put it simply, QC10's intent is to position themselves as the one PCC-well you'll ever need to draw water from.

Quarter Circle 10 specializes only in AR pistol carbines, with chamberings in 9mm, .40SW and .45 ACP.  They have lowers compatible with Glock, Colt, Sig, and Mp5 mags.  There are other options as well (side charging versus rear charging, skeletonized receivers) but the bottom line is you won't find any rifle caliber specific parts here.

Quarter Circle 10 Side Charging QC-5 Builder's Kit

QC10 sent me a “QC-5 builder's kit” with an MP5 mag-compatible lower, side-charging upper, 5.5″ 9mm barrel, G9 bolt assembly and adjustable-weight buffer.  Knowing how few and far between short AR handguards are, QC10 even offers M-LOK and Keymod handguards as short as 4.44″, and was kind enough to include one for the article.

That leaves the trigger assembly, takedown pins, grip and receiver extension.  I used a Geissele Super 3 Gun (S3G) trigger,  SB Tactical PDW brace, Mission First Tactical pistol grip and a few assorted extras to finish the parts list.  Side note: the Geissele S3G wasn't on the "approved trigger" list by QC10, which meant it was a known risk going in.  It ended up having reset issues and was swapped for an ALG Defense ACT trigger.
QC10 build kit, minus buffer assembly and extra weights.

Assembly of the QC10 kit is pretty painless.  Starting with the lower receiver, we see it comes with the mag release and bolt stop already installed.  Quite conveniently, the bolt stop is held in place by a threaded pin, not a hammered-in roll pin.  If you want to swap in an oversized paddle, the time and effort needed is dropped significantly.

QC10 PCC
QC10's PCC bolt stop is held in place by a threaded pin, not a hammered-in roll pin.

That leaves the trigger assembly, takedown pins, grip and receiver extension.  I used a Geissele Super 3 Gun (S3G) trigger,  SB Tactical PDW brace, Mission First Tactical Engage pistol grip and a few assorted extras to finish the parts list.  Side note: the Geissele S3G wasn't on the “approved trigger” list by QC10, which means it was a known risk going in.  It ended up having reset issues and was swapped for an ALG Defense ACT trigger.

Installing the front takedown pin can be a little frustrating for those who aren't dexterous. I like to use a flathead screwdriver to hold the detent pin in place until the takedown pin can slide over it.  This reduces my pin-launching events by about 99%.

QC10 PCC
I like to use a flathead screwdriver to hold the detent pin in place until the takedown pin can slide over it.  This reduces my pin-launching events by about 99%.
QC10 PCC
The rear takedown pin is much easier, and its related spring is held in place by tightening down the receiver extension of the SB PDW brace.

The trigger assembly and grip are pretty “drop-in”, especially with the use of Geissele's trigger and hammer pin placeholders.  These shortened pins hold their respective assemblies together and align until you slide the permanent pins in through the receiver holes.  The grip is held by a single screw, while also holding in place the safety selector, detent pin and spring.  Finished, the lower looks great!  We still have the buffer spring and weight to cover in an upcoming section.

QC10 PCC
Finished, minus putting the bolt catch back in. Was waiting for an oversized one, ended up using the stock one.

The upper receiver of the QC-5 is even easier to put together.  While I used a receiver block, the QC-5's unique interior geometry meant that I couldn't use the block's pins to hold the receiver in place.  Just a small precaution: hold onto it when torquing!  There is no gas block, gas tube or ejection port door to be concerned with on the QC-5.  Simply place the barrel into the upper, apply a little dab of Loctite to the barrel nut threads and torque it down.  I usually go to around 40 foot-pounds.

QC10 PCC
The upper receiver of the QC-5 is even easier to put together.

The handguard supplied by QC10 has an anti-rotation horseshoe, that indexes on the (non-present) gas tube.  I still installed it to prevent an unsightly gap.  I slid the handguard onto the barrel nut, aligned the top rails and used the pair of clamps (with Loctite) to affix the handguard to the nut.

QC10 PCC
The handguard supplied by QC10 has an anti-rotation horseshoe, that indexes on the (non-present) gas tube.

When it came time to choose a muzzle device, I had to go with my favorite.  Flash suppressor?  Muzzle brake?  Nope, a suppressor.  Call it a silencer, can, sonic reducer or whatever you please: just don't catch me at the range without one.  Since I picked up my first in 2005, I keep my guns quiet whenever possible.

Installing a fixed-barrel spacer into my AAC Ti-Rant 45 (with 9mm adapter piston) took only seconds, and means I won't risk damage to the suppressor, which is OEM set up for a tilting barrel handgun (Glock, 1911 etc.).  Slide the modified bolt assembly into the receiver (no charging handle here with a side-charger), and make sure to depress the little proprietary catch at the back of the upper when assembling with the lower.

QC10 PCC
Slide the modified bolt assembly into the receiver (no charging handle here with a side-charger), and make sure to depress the little proprietary catch at the back of the upper when assembling with the lower.

Finally, let's cover the adjustable-weight recoil buffer.  It comes with 4 tungsten weights (and pads) installed, as well as 4 steel and 4 aluminum weights as extras.  An allen-head screw/pin holds the blue rubber shock pad in place, which in turn holds the weights and pads inside the buffer.  QC10's handy included chart indicated that a suppressed 9mm should have 8-11 oz of weight in the buffer.  To get there, they recommend using all 4 of the steel weights, which brought it just barely to 8 oz.  I changed out one steel for a heavier tungsten weight, as I'm going to be testing this PCC with some hot ammo.  This brought the buffer up to ~9 oz.  Standard carbine spring to go with the buffer and into the receiver extension, and the gun is done.

QC10 PCC
It comes with 4 tungsten weights (and pads) installed, as well as 4 steel and 4 aluminum weights as extras.

The QC-5 comes in a 5 lbs 9.1 oz, not counting the suppressor or optic.  A good chunk of that (18.1 oz) is tied up in the SB PDW brace, but the gun balances very well.  Someone wanting a lighter overall package could certainly pick a different brace.

QC10 PCC
The QC-5 comes in a 5 lbs 9.1 oz, not counting the suppressor or optic.

I topped off the PCC with a Vortex AMG UH-1 (as well as the AAC Ti-Rant), and will also bring a Nikon low power variable optic out to the range to see how this think performs!  I have a good bundle of ammo on-hand, so stay tuned for a range day update.  So far, this is looking like an interesting (and more modern) MP-5 alternative.  Price on this builders kit (both receivers, barrel, bolt assembly, buffer assembly) is $949.95.

Use coupon code AMMOLAND for 15% off!

Rex Nanorum

@Rexnanorum


About Rex NanorumJens Hammer

Rex Nanorum is an Alaskan Expatriate living in Oregon with his wife and kids. Growing up on commercial fishing vessels, he found his next adventure with the 2nd Bn, 75th Ranger Regt. After 5 tours to Afghanistan and Iraq, he adventured about the west coast becoming a commercial fisherman and salvage SCUBA diver, rated helicopter pilot instructor (CFII) and personal trainer, before becoming a gear reviewer and writer.”

Rex Nanorum

@Rexnanorum

 

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    RobOlen BiehlRex NanorumBobRattlerjake Recent comment authors
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    Rob
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    Rob

    Yeah, I’ll just buy 2 Kel tek sub 2000 for that price!!!

    Olen Biehl
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    Olen Biehl

    I would love to build one of these in 5.7×28 like the Banshee. I find that caliber zn outstanding choice for practically any target. Animate or inanimate.

    Bob
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    Bob

    The author didn’t state, but if you’re wondering the kit is a whopping $1000.00 before you buy the rest of parts needed!

    AR PCC manufacturers need to understand to be competitive their price point needs to be in same range as Ruger’s PCC around $500 retail, less for shelf price.

    Rattlerjake
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    Rattlerjake

    Just wait a little while, the price will drop when they go bankrupt!

    Jeffery P
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    Jeffery P

    I plan to make an AR-9 instead of buying one. Would you say this is a good first-time project for a beginner builder?

    Bob
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    Bob

    Great idea, but this kit is away over priced. Shop around complete AR 9mm PCC are a dime a dozen for around $700. You should be able to build one for less than $500.

    Notlima
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    Notlima

    What Bob said. QC10 has some great stuff, but you are paying a huge premium for that name.

    You can get quality parts for your build for a whole lot less by shopping around. And, save yourself some additional money by going with a Glock Mag compatible lower for your PCC. The MP5 mag lowers have a ‘neat’ factor, but Glock mags are reliable as hell, cheap to buy, and proven to run in PCCs lowers made for them.

    Bob
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    Bob

    If you don’t want to run a dedicated lower for a PPC build there a a couple of companies making mag well inserts that fit a standard AR lower. Depending on the insert you can run Glock, S&W M&P, Colt or several other brands of magazines.