I've posted this thread for those of you considering a 22lr Conversion Kit for your Sig 516. After a lot or research, I ended up purchasing a Stainless Steel CMMG 22lr Conversion kit. Since I live in Kalifornia, it was a major issue just finding 10 mags that would function properly. Here's what I ended up with, and it works flawlessly in my Sig 516. The CMMG is major quality, much better than the Colts and Ceiner Kit's I"ve used in other AR's. It can be found for about $175.00 on Gunbroker. Finding the 10 shot mags were almost impossible, CMMG was out of Stock and the only place that had them was Joe Bob's Outfitters (Black Dog mags), only $11.00 instead of $30.00 from CMMG (if they had them). They are the full size Mags for the AR15, not the stubbies with inserts. They are plastic, but work with absolute perfection. Being that the CMMG is a blow back design, the gas port/Piston is irrelevant. If its an old CMMG unit, you just remove the Gas Piston, but if it's a newer Evolution Unit, CMMG has already machined Bolt Carrier down, so you don't have to remove the Piston Rod. It's a beautiful Combination your going to love. Ps. It will shoot 3-5" groups at 100 yards, about the same as my Mini-14. What's really nice, the Sights do not need to be adjusted, it pretty much shoots dead on using the same setting as my 5.56 ammo. Hope this info helps. Jack B.