A closer look at the MGI QCB-D Upper Receiver

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 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.
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