Major difference in the blowback vs gas operated uppers is not only the function on how to get energy into the BCG to get it moving, but the shape of the Bolt / Carrier. The blow back is a one piece design where the shear weight of the unit delays opening. A simple and effective design. The issue is there is a point where where you just cant get enough mass into the BCG to delay the opening of the bolt while not beating the death out of the upper. Our Tok blowbacks in a carbine stock are pretty ruff. Using rifle stocks allows a little more time to smooth things out. But, I'm getting off track, lets get back to the shape of the BCG. The gas bolts have the ability to engage and rotate / lock into the barrel extension. The design creates a gap between the bottom of the carrier and the bottom of the bolt when then the BCG moves backwards. With the .223 and most rounds with a shoulder, this gap does not create a problem. When we use straight wall cases and start shortening them up, this gap allows the bottom rear portion of the bolt lugs to catch on the rim of the case. As we get into these "lower power" rounds running on gas we need as much power as possible into the carrier to get it moving. Carrier drag, mass, buffers, even hammer spring tension plays a part in this. We have made big gain in these issues with our piston systems but we still need things as smooth as possible. So, what does this have to do with a 1911 mag? Same as the Uzi mags: the angle of presentation of the round in the mag vs the shape of the BCG. The blow back carriers relying on resistance and the one piece shape all work in favor of these issues. Gas systems work against them. For our Gas9 system with CUZI adapters, we level out the follower to make the rounds sit a bit flatter in the system. So this is what we are looking at with the 1911 mags, the angle of presentation in the gas systems. The ProMag 45 Uzi mags work well with our 45 adapters. In todays world, the availability becomes the issue so the option of the 1911 mags is being looked at. Then there is the mag retention portion of all these conversions....... Have a great Sunday!
Got a couple of M3 Grease Gun mags in to see how much we would have to modify to use them. Without having to broach a bunch out of an AR magwell we'll take a look at what the options are. They are even wider than Glocks.