For years now I’ve always been intrigued by MGI’s QCB upper receiver. The ability to quickly swap barrels without having to change optics, carriers etc seems like a good idea.

But alas, my research for reviews was unsuccessful, I couldn’t find anyone that was actively using one and had some reviews or thoughts on it.

I contacted Cory at MGI Military, he agreed to send me a unit to review. If I didn’t like it, I was free to return it at any time. And the price was right as well. So I agreed, and placed the order. Within 20 minutes of me placing the order, April at MGI sent me the tracking number.

The unit came in a small box, well packaged with a color instruction sheet.
Rob, my UPS driver and I looked at each other in disbelief. That’s it? It doesn’t weigh anything! After I removed it from the box I found that is was very light indeed. 1lbs and 11Oz. to be precise.


Here is the upper, along with the instruction sheet, as I took it out of the box.

Operation is quite simple:

   * On the bottom of the receiver, flip the locking bar up. This may be a bit tight, some leverage can help.
   * Once the lock bar is up, slide the plastic retainer piece forwards. It’s cut so that it slides forward over the picatinny rail, exposing the locking arms.
   * Turn the locking arms 90 degrees outward. This unlocks the barrel.
   * Remove barrel.

Inserting a barrel is equally simple, follow the steps above in reverse, and the upper receiver is ready to shoot.

A few first thoughts, so far:

   * I’m very impressed with the fit, function and finish of the unit. It fits all my lowers well, without any play.

   * One thing that I was curious about, was how the gas tube would line up. The upper receiver has a much thicker wall, and just forward of it, a ring is inside the free float tube, assisting in guiding the gas tube to it’s proper position in the receiver.
   
   * As we all know, picatinny rails can be quite sharp. This is usually easily fixed by adding covers, whether they be slim ladder style or full panels. However, with the locking bar cover sliding over the bottom rail, adding rail covers would mean that the covers would have to be peeled off before a barrel can be removed. This is also the case for vertical front grips, unless of course they have a quick release on them.


Upper receiver part, not much different from a normal receiver


The Locking System, side-view


Top view of the receiver.


Bottom view of the locking system.


Locking slider open.


Locking arms open. The barrel can now be inserted or removed.


A view inside the receiver shows the massively reinforced forward wall with guide hole for the gas tube.


Inside the free float tube.


The barrels only need a barrel extension (most come like this), a gas tube and gas-block or Front Sight base of some kind.


7.5" Barrel installed.


11.5″ barrel with Gemtech M4-02 installed.


I now have around 2000 rounds through the MGI QCB-D upper receiver, and I must say, all trouble free, as far as the upper goes. All rounds were in full auto on the M16.
The upper has really proven to be a very useful, versatile add-on to any rifle.
The ability to unlock a hot barrel, “shake it out” of the the receiver, and install a new one in no time at all is very handy.
Pro-tip: Make sure everyone around you knows the barrel is hot, or nasty burns will be the result of curious fingers…

I’ve only had 2 different barrels in the upper, a White Oak Armament 10.5″ and a 7.5″ from a DPMS Kitty-Kat. Both fit well, locked in snug and performed flawlessly.
The 7.5″ did require a low profile gas block. When installing barrels in the MGI upper, the hand-guard cap needs to be omitted.

On the barrel lock up:
The barrel extension flange is what the MGI upper locks on, and if it isn’t within a few thousands of .131″ (Rock Island Arsenal blueprints) locking issues may occur.
I found that the barrels I installed to lock up tight, with the exception of a new 7.62×39 YHM barrel I purchased. The flange on it measured .127″.
While this will not an issue on a standard barrel nut setup, it is too thin for the MGI, and the barrel will still be loose after installation. The barrel could literally be rocked back and forth, with an extension only .004″ out of tolerance.
MGI can adjust the tension on the locking cams if desired, but an in-spec barrel extension will then be too thick, causing locking issues as well.

About the rail:
I found the rails to be as good as any, I mounted an EOtech on it, as well as an ACOG without any issues. I did end up just using a carry handle on there as a sight.
The rails not in use were covered with Knight’s Armament rail covers. These can, by the way, be locked on non-KAC rails by gently prying the tab up with a small screw driver.

The biggest downside I see from the MGI QCB-D upper is the inability to mount anything to the bottom rail. Ideally, the sliding lock needs free movement to function, so covering the rail section in front of it renders the whole system useless.
Of course, anything can be removed, especially a nifty LaRue or ARMS disconnect vertical front grip, or a light with quick disconnect, but it’s an extra step, with more loose items laying around to keep track off.
I really think that a slider with a rail cover section on it, to protect the hand, would be an addition, or even a slider assembly with a VFG integrated to it.
Perhaps MGI can get with Magpul for a custom Angled Grip.
Just a thought.

Corey at MGI Military was right, I do love this thing, and I will continue to use it extensively.





I wrote this write-up in separate posts on my humble firearms project blog, which explains why it's not a continuous story...

Thank you! I've been eyeing one of these for awhile, I was waiting for some of the AK74 lowers to become available before I pulled the trigger on a complete setup. I wish he would have sent a rifle rail extension as well, I would like to see how well that works. Any chance we can see a pic of the inside with the locking levers closed?