Hi guys, I have a 21SF that I am interested in fitting up to be able to shoot 10mm. I have a 22lb. ISMI recoil spring and a non-captured SS guide rod. I have a new G20 15 round mag. and it fits into the 21SF mag well like a glove. I'll be getting a few more of those, by the way. I've talked with Kevin at KKM and he said that after I order G21 drop-in to 10mm, 6" barrel, all I'll need to do is a little filing work, per his instructions on the 21SF's extractor and I should be good to go with shooting 10mm and 45 as well. For those of you who have gone this route, is it worth it and would you recommend I do it based on you experiences? I'll be using this caliber for hunting and some longer range target work. Some pics of your pistols with this set-up would be nice too! Thanks.