If Ruger ever got Promag to make 'em, I hope they were smart enough to switch back.
Colt tried the same thing with their 9mm SMG mags for ARs, Metalform made them for years and they switched to another company like ASC or CProducts, and immediately had issues. Within a few years they switched back to Metalform.
Promag is hit or miss with me, although if they're the only hi cap option I'll take a chance. Sometimes a stronger spring or tweaking feed lips is all it takes. My Promag S&W Shield 9mm 10 round has never jammed and while it's obviously not as stout as S&W factories, they work. I've also chunked a few Promags in the trash over a lifetime.
Anyone tried the new Tapco gen 2 30 round polymer mags? I know the gen 1s were terrible but I see good things about the gen 2 with the steel reinforced front. I've had good luck with Tapcos in AKs & SKSs for good cheap disposable range mags.