Bought one of those red HKS speedloaders that was clearly marked for use with Ruger Mk l and Mk ll magazines.... decided to try using it on a Mk lll magazine even though the loading button is on the left side of the magazine rather than the right side. It hung up on that projection on the left side of the magazine near the feed lips. Took a small rat-tail file and made a groove in the HKS speedloader to clear that projection. Wow... darned if it didn't work !!!