Looking at the clearance required in a couple of my metal mags, it looks to me like the ribs could be pressed out enough to get the proper clearance. A simple steel "die" in a relatively small hydraulic press should do the trick. 5.56-like clearance could be gained using a simple flat steel plate without contacting the forward feed lips so it should be simple to just flatten the ribs a bit. For that matter, I don't see why the entire length of the rib would need to be adjusted. It seems like only the top of the rib would need adjusting so as not to adversely affect the feed of the top round.
Of course these rib mods might make the mag less than ideal for 5.56 or 300 rounds that have been loaded to have the bullet ogive touch the rib but, other than that, is there a disadvantage to this approach? I guess it might fly in the face of an AAC design goal too, but what do I know! I now have all the parts to build my 300 Blackout pistol but still need to get to it and stop daydreaming.
