Will still leave marks on the magazines
Brownells Feed Lip Tool This simple tool is used to adjust the feed lips on AR15/STANAG magazines. Sometimes the feed lips are bent, too tight, or too loose. There aren't any instructions on how to properly use this tool, but using logic I was able to figure it out. I'd say that this tool isn't totally perfect. It can/will still mar the feed lips slightly especially when opening the lip clearance. It left half-moon markings on the feed lips although there wasn't any physical damage. It is a fairly basic tool, and I'm sure you could make your own using a thick screwdriver and a die grinder to cut the slot. This tool wasn't too expensive, so it was a good and inexpensive addition to my AR15-specific tools. Overall: 4/5 stars, instructions or techniques to assist the user would be great. It still marred my magazines slightly.
Bad sample?
Picked up to reprofile some mags for 458 SOCOM. The metal at the little channel for the 'lip' portion was squashed out of form on the first mag. I'd guess the metal was just too soft for the job. Maybe this was a bad sample from whoever makes this for Brownells. My Aluminum feedlip tool from MPA has held up for several mags with only minor deformation. That should say something about the metal used in this tool. Brownells was great in getting the return processed. Thank you.