How does the USGI .22 trainer compare to the Ceiner kit?  I have the USGI but haven't fired it yet, is it semi-auto or single shot?

What's the history behind the US Military's use of .22 conversion kits?

The US Army has the kit but rarely, if ever, uses it to my understanding. I've never seen one in the active Army. I do know a guy in the Navy who used one for their qualification on the M-16 - I believe the Air Force may do this as well. The Army generally sticks to real training though with 5.56MM rounds. The .22lr kit has it uses but it obviously cannot duplicate a 5.56MM round. I would imagine the Ceiner kit is better then the USGI - just more expensive. The kit replaced the existing bolt/bolt carrier and the magazine with a special .22lr magazine. The weapon will then fire in blowback operation. If no malfunctions occur with jamming, you should be able to fire semiauto no problem or full-auto in an M-16. Jon  

Hay Smeg, I got m cliner about 2months ago, and about 3000rnds later.  Man if you like a 10/22 and like your ar you'll have a ball with the convertion kit.  Mine in my bushy carbine will shoot shot for shot with my SS 10/22.
 I put a jewel trigger in my AR Rifle and use the convertion for trigger and position practice.  
 My cliner hasn't had a flaw with any $1.50 a box hi vels, and with Federal bulk packs the ony time she misses is when the slide needs a drop of oil.  Otherwise she rock and rolls.  The only complaint ive heard about the cliner MK111 is the 30rnd mags just don't hold enough,haha.
 Show ya how I use it alot, Our 25yd range guys pistol shootthe clay pigeons alot.  So I clean up ll the little peices with mine.  I mean if you can see a peice I can hit it.  Glad I got one.  JB