A buddy of mine just bought a parts gun AR: Bushy lower & who knows what upper. The lower is an A2 config but the upper is the short barrel M4 config, 16" (I think).
His problem is it only fires one shot at a time, fails to cycle IOW. It will eject but apparently doesn't come back far enough to pick up the next rd to feed.
He bought a collapsible stock & tried that, same result.
BUT: if he puts the spring & shock buff from the collapsible stock in the A2 buttstock, the GD thing works fine!!!!
My guess is the short barrel & gas system isn't enough pressure to send the bolt carrier back far enough with the full spring on the A2 stock but it also won't work in the collapsible stock which probably has the same/equal pressure.
What's the solution to this dilemma? He wants the collapsible stock for his wife to use. Does he go with a different recoil spring? Does he cut off a coil or two until it works? What?
I've checked all the obvious problems with the gas tube being pinched, gas rings on bolt, etc. etc.
Thanks in advance.