I had the opposite luck with the synthetic mags - garbage!
I bought three Cobray mags some years back, and was very displeased. But, I hate to return anything, so I took the challenge to improve them.
Had to do the following:
A) The followers were the wrong angle - the bullets hit the bottom of the chamberface. I built them up with JB Weld and a strip of Stainless Steel sheet metal.
B) The inside of the mag body had some mold lines, making the follower stick. More JB Weld, and a good sanding & polishing inside, including sides of the followers.
C) The most serious problem, the feed lips were way too thick and squared off. Bolt couldn't move forward or back. I filed, reshaped and thinned the feed lips.
After essentially re-engineering the mags, they went from 0% function to about 90% function. I still can't trust them in a serious shootout.
These mags were half the cost of the steel ones - until I add in the labor to fix them!