I know there are alot of dreamers, doers, and tinkerers out there in the AR world, has anyone given thought to a dedicated 22 MAG upper.  Aside from devolping a new magazine, would it be possible to take a dedicated 22LR upper and rechamber it? Only difficulty would be making a reliable magazine.  I haven't seen any of the DPMS or other 22LR dedicated mags to know whether there is enough room to open it up for the magnum. This was given to me as food for thought, so I'm looking for other thoughts as to possibilites.

I built a 22 magnum upper that seems to work just fine but just like you said, the magazines are the problem.
I started out with the idea of modifying a standard 22 conversion unit to take the 22 magnum round but ran into a few problems.
the distance the 22 bolt moves rearward needs to be increased, the ejector needs to be moved rearward, the pocket in the bolt face needs to be opened. There is a need for more bolt mass and/or much stronger spring. I completed the conversion and tried it first in my Colt and found the 1/7 twist just tore up the thin plated jacket. I tried it in a 1/9 twist and had the same problem. I then tried it in a 1/12 twist and it seems to work just fine but time will tell. The normal twist for the 22 magnum in commercial rifles is 1/16, the same as for 22lr.
I used the M261 GI conversion unit to work on -- it has an extractor helper and I believe it is very important in the unit's operation.
The magazine is a Marlin 7 round unit that I built a carrier block for and slide it into a junk steel 20 round AR magazine. It works but not as well as I would like.
I think the next step might be for me to try the Ciener unit and use a 22 barrel made with the chamber in it and designed to work with Ciener -- either from KKF or maybe Kuehl. That way I can get the correct 1/16 twist.

That's useful info thanks. I thought about trying to adapt a DPMS dedicated but didn't want to spend $350 on the upper only to screw it up or find out that it wasn't possible. I guess I'll have to get one and look it over at the areas you mentioned and do some pondering before modifing.

I had hoped that Kurt at KKF would do some work on a Ciener unit and turn one into a 22 magnum unit but he had the same problem -- what to use for a magazine. There was one company that built a 22 mag upper but you had to buy the whole thing, not just the barrel and bolt mechanism. I like screwing with things like this but I can't say at this time it is something that anyone else would want.
This is a picture of the rifle and below it is a picture of the mag setup.
[img]http://images.ofoto.com/photos412/3/7/50/50/93/0/93505007305_0_ALB.jpg[/img]
[img]http://images.ofoto.com/photos412/3/7/20/40/32/0/32402007305_0_ALB.jpg[/img]

I guess maybe I should start there with the magazine, if I can get that whipped then the upper shouldn't be a problem. Thanks for the info it give me some where to start.

I'll have to say I just picked the first mag I could find and built the unit around it. I have Ciener units, the M261 unit and a USAF unit and decided that the M261 looked like a good candidate for this job. I would love to use a Ciener unit but I hate the idea of messing with one of my good Cieners because once it's done the unit is no good for regular 22lr's. The Ciener also has the long spring guide tube that would need to be shorted and a different spring used. the reason for the new spring is the original spring, when compressed, still won't allow the bolt to move back far enough. I may still try to find a cheap Ciener to modify.
Let me know if you find any good 22 magazines to use. I though about the Grendel 30 round mags but they are way too wide to be fitted into an AR-15 magwell.

I guess I need to bite the bullet so to speak, buy some different mags, ammo, maybe a dedicated upper and just go for it. The nice thing is that the guy who wants this said he would fund any R&D so I really have nothing to loose other than time.

I'd start with a Ciener kit.  They're still in production so parts are easy to get if you mess something up.  The rail plate is a simple flat piece of steel so it'd be easy to modify or replicate with the ejector farther back.  If/when you get the kit working you can add a dedicated barrel to it.  (With a KKF barrel you could even use the same barrel for .22LR since his still use the chamber adapter.)

The only magazine that comes to mind are the Marlin ones.  You should be able to find a way to insert them into a .223 magazine, or modify a magwell block from a Ciener mag.  The hard part will be getting the angle and position right for reliable feeding.

Mike_L,
 I also believe the Ciener can be made to work and may work a lot better because of the type of chamber adapter that the Ciener unit has. I found another Ciener unit for sale that I was going to modify but I think the seller got some better offers and it suddenly came up "SOLD". I didn't want to screw with the two Cieners I already have so I went with a M261 unit that I have, since it never really seemed to work that well for me. I have a KKF 22lr barrel that I can use for the Ciener in 22 magnum -- some people don't like the idea of running a 22 mag bullet down a 22lr barrel but it does work. The final configuration would be a nice barrel that eliminates the ciener chamber adapter like a barrel from Kuehl.

I want to get away from the whole adapter deal, I want to build a dedicated 22 mag upper.  If need be I'll turn a barrel chambered in 22mag and install the barrel extension.  I want to look at the DPMS uppers to see if I can just rechamber and make a mag.  No one local here has any to go look at and take apart.  I want to ponder over their bolt and the whole works.  If nothing else then I'll go to M261 or Ciener and work from there.

I started with the 22 magnum conversion unit just as an idea but after getting it set up and trying it in standard AR barrels I discovered that the thin plated jacket didn't like fast twist rates and they would some times peel off. I realized that the conversion unit idea wouldn't work so I tried a 1/12 twist Colt pencil barrel with the 22 magnum chamber mounted in it for testing and it seems to work fine. This is when I decided, like you did, that a dedicated barrel must be used. I don't want to go to the expense of a custom barrel right now with out working out the magazine thing first.

I think that will be my first priority will be the magazine, regardless of what barrel, and action components I go with.  If the mag doesn't work reliably then nothing else will work either. Thanks for all the ideas, we might be on to something here.