John,
I really don't believe the Metalform mags is your problem.
The reason I say this is I've used Metalform 9mm and 38 super mags to feed the custom 9mm hand guns I've built.
The custom 9mm in the picture was test fired with five different brands of factory ammo and one of my favorite 9mm handloads.
I used four different Metalform mags to feed the gun, two were 9mm mags two were 38 super mags, I never had any failures.
I believe you may have a gun problem so I do not recommend you spend more money on mags.
It sounds to me that the gun may still be to tight and you may have a barrel timing issue.
I also feel your 10 pound recoil spring is to light.
Best Regards
Bob Hunter
www.huntercustoms.com