.22 is alot less money than 223 of course.  Is it worth shooting a 22 over a 223 as the kick and feel are different?  Is it a good thing to in general changing the cal to a 22?  The gun was built to fire a 223.

Also, I forgot to ask, if they are good then who makes a good one (don't want junk in my 1,000 dollar rifle) and where can I buy one?

Thank you
FireBlade

Jonathan Arthur Ciener,Inc.
8700 Commerce Street
Cape Canaveral, Florida 32920
Ph. 321-868-2200,Fax 2201
They make the best conversion kit on the market in my opinion. You can get it in AR15 or M16 version. It comes with a 10 round clip. You use  to be able to get a 30 round clip but the high capacity ban done away with that. It is a waiting list when you order of about 6 weeks.I have also seen some on e-bay for sale. I think the price for the kit in AR15 style is $139.00 + shipping. The change over is real simple. All you have to do is take the bolt carrier out, change the clip and start shooting. Same way changes it back to .223 cal. About a minute of your time is all it takes to change it over. How simple can it be. I have one and love it.

The only one commonly available is the Ceiner, which is the kit that most dedicated uppers are built around.

The Ceiner is a sound design and the unit seems to be made with good materials but Ceiners often need a couple of hours of gunsmithing to make them work decently and reliably. There is a small laundry list of little things that need to be done to them.

If you use copperplated bullets the leading problem isn't a worry.

In a regular AR, they are great for hunting rabbits and plinking.

You can get a Ciener from Brownells for about $130. Well worth it. Bit of advice, if you're shooting regular leaded 22's, fire a couple 223's just before you head home or stop shooting. The 223's will help get some of the lead fouling from the 22's out of the barrel and blow the nastiness out of the gas tube.

The Ciener is the only one in current production.  It's available from many sources.  Bushmaster lists it in their catalog.  I got mine from Model 1 at a gun show.  There are at least three other styles: Army M261, Air Force M261, Colt.  None of the magazines are interchangable.

Accuracy won't be as good as with a regular .22 like a 10/22 or Marlin, but still good enough for plinking at short range.  

You might also look at the .22 uppers from DPMS and CZ.  They have proper .22LR barrels with correct diameter and twist.  More expensive than a kit, but cheaper than the dedicated uppers built around the kits.