Anyone have success with the plaslic lip mags? I have read a bit and I recall one fellow saying he built up the rear area of the mag with epoxy to snug up the fit. I fired about 300 rnds yesterday with the factory mags, no problem. Used the plastic mags, 2-3 jams each time I loaded it up. I have a good variety of aftermarket internals now, and it works great until I use these mags. Are the metal lips better?