kzin - Black Dog sells a specific magazine designed to work with the M261 conversion unit that CLE provides with their 22RF uppers, and the only one they show is still in the 30rd GI form. The feed lips on the M261 mags don't extend upwards nearly as far as the ones they show in the link you provided. I could always call to see if there are any new developments for the M261-compatible mags...but I bought the three I have only a year or so ago.