Re: Other AR 22 conversion kits, besides CMMG?
I own and use a Spikes Tactical conversion. After some very slight tuning when I first got it, it has been absoultely flawless for THOUSANDS of rounds. Plus it is chrome plated, which you will greatly appreciate when it comes time to clean. Plus the people at Spikes are great to deal with, and go above and beyond, if you need help.
A friend has one of the older Ceiner kits, and it basically a single shot conversion. He was toyed with it for years, and e very once in a while he can get off 3-4 rounds before it jams.
I have no personal experience with the maker, but hear that his customer service leaves a ton to be desired.