LWD used to offer a G21-10mm conversion. It is our experience they will fail to extract about 10% of the time. The majority of extraction problems were ammo related, none the less it is still a problem. In my opinion, 10% failure is too great an issue to ignore, and certainly time consuming when it comes to dealing with you the customer. We discontinued selling this conversion because of these issues. We advise our customers to simply switch top ends. This way you are assured 100% reliability.