Well I got a couple of barrels for my MGI Quick Change upper, one being a used 300 Whisper Barrel with hole drilled for a carbine, the other a bull barrel in .2.23. This was mated to a collapsable stock lower I had.
Played havoc trying to get it to cycle reliably with light loads. Would continually short stroke. Finally picked up an adjustable gas block and shortened a rifle length return spring to 3 coils shorter than the carbine recoil spring. Problem solved.
What a treat to shoot. Going from .223 to .300 takes all of about 3 minutes, and this includes changing the recoil springs. The looks you get at the range are priceless. I through 2 levers, grab the barrel and yank it our of the upper.
Have not had a lot of time to dial it in but appears that the change in point of impact when changing the barrel out and going back to the original (Example, sight in the .223, swap it out for the .300, then go back to the .223 again) is about 1 inch at 100 yards. I think that is pretty fair. I am also finding that when swapping barrels the windage within 1 moa on either barrel but the elevation needs to come up 12 inches over the .223 zero
Anyhow once I get it all worked out and set up I will try to get some pics posted...
Have a Great Day Folks....
DonT
Quick Change Upper....
Threaded Mode