Since posting my recent video on the new Air Force GAU-5A rifle, I've had a number of questions by viewers asking me, "Why use a detachable barrel when you can unpin the upper from the lower and stow it that way?"
People have been asking this question since the advent of QD barrel assemblies for AR15's. Given detachable barreled rifles and pistols have been around for years, I have assumed this question would have slowly dissipated over time, but it hasn't.
QD barrels on AR15's significantly reduce the over all length of the stored rifle/pistol when compared to rifles stored with the uppers unpinned from their lowers. Let's take a look at the GAU-5A a bit closer and take some measurements.
The assembled pistol above is about 28-1/2" in overall length. That's pretty short by conventional rifle standards (again, this is a pistol with a brace vs. a stock). However, the Air Force needed to fit a carbine into a very small pouch as part of the currently issued ACES II survival kit that stores under the ejection seat of fighter aircraft. In its configuration above, this clearly isn't going to work. Here's a picture of the new GAU-5A in the ACESII pouch it's required to fit into if it's going to fit under the ejection seat.
Yup, 28-1/2" isn't going to cut it. That's why the Air Force had to get creative. But wait, what about the idea of simply unpinning the upper from the lower and storing it that way? Let's take a look at the overall length of the same gun with the uppers and lowers separated.
We are at about 21-1/2" if it were to be stored this way. Clearly this isn't going to fit into the ACESII bag shown in the preceding image. Now lets take a look at the GAU-5A disassembled for storage under the pilots seat and see how long it is.
Now the entire package is just over 15" which allows it to store neatly in the ACESII ejection seat survival kit. There is over a 6" difference between removing the barrel from the upper receiver vs. unpinning the upper and lower. Hopefully this illustrates why the Air Force wanted to QD barrel on the new GAU-5A and answers any questions you may have regarding the purpose and/or utility of QD barrel systems.