I have a 10.5 AR15 Pistol.....

Would it be more beneficial to get a .22lr dedicated upper? or just a cmmg .22lr conversion kit? I believe the conversion kit would be a lot cheaper......

I have both and was disappointed with just using the CMMG in a 223 rifle.  The CMMG dedicated barrel was a very worthwhile purchase for me. 

A dedicated .22lr upper will be more accurate and you won't need to be concerned with the gas port and tube getting carboned up.

A conversion kit is cheaper and a few .223/5.56 cartridges fired after every few hundred rounds of .22lr will cleaning out the .22lr gunk

It's really a toss up. For me, the accuracy with a dedicated .22lr upper was the key

Take a look at this thread in the ammunition section her on ARF.Com.  There are accuracy reports in this thread which might help you decide which route to go.


http://www.ar15.com/forums/t_3_16/712506_22LR-accuracy-data-for-multiple-loads-with-CMMG-conversion-kit.html

Since it's not my money, get the dedicated. =) But it depends on how accurate you want the rifle/pistol. 223 barrels are larger then 22lr bullets and the twist is way off (1:7 vs 1:16).

I went with the dedicated upper  (which some how grew a lower) then recently built a 9 inch pistol AR22. so far the squirrels in my on my property HATE it.

Only you can determine what is more beneficial for you.  In true arfcom fashion though, why not get both?

Or, start with a conversion kit and if it doesn't work for you, then get a barrel and collar and turn it into a dedicated upper.

I have a handful of Ciener .22 kits.  I have a few .223/5.56 guns that shoot pretty good with them.  I bought barrels and collars and made a couple of them into dedicated .22s.

I tried both... sold both and SBR'd my 15/22 which runs exceptionally well.

Here are facts about your upper: The bore diameter is slightly larger, and your sights are calibrated for .223/5.56. With that said, the bullet won't go where you used to aim and it will drop differently. How differently? Well you'll just have to test for that. For me, at 25 yards, I aim just below the 300 tick of my optic. It hits that area every time. Comparing to a 5.56 round, it hits the 300 mark at that range so I am nearly identical.

What I learned is that if I shoot the .22 dropin, I can shoot it all day long. No clogging, nothing. The gas tube can be blasted out by simply shooting a few .223.

On the flip side, I learned that shooting cheap Tulammo and then shooting the drop in is disastrous. For some reason Tulammo clogged up my barrel, I then put the conversion in and rounds were shooting wildly all over the place (talking about 5ft off in random directions). I had to clean the barrel for days. I'm still shooting Tulammo and the drop in kit, but I'm just not doing it together.

If you shoot the drop in conversion kit, and then shoot a few .223 afterwards to clean it, you should never encounter a problem.

My conversion ended up a dedicated.

Pay now or pay later.

It's very difficult to keep that conversion a conversion in my opinion.

Neither.  I never had much luck with my dedicated upper.  I'd get one of the M&P 15-22 rifles.  More reliable and the mags are nicer.

I ended up building a 10/22, but the 15-22 rifles I've shot were 100% reliable.

^This, would you fire .223/5.56 in a 1:4 twist barrel?

Oh, here's another thing for you to consider. It's really easy to clean the dedicated upper than it is cleaning the conversion.

For the dedicated, most of the fouling is in the barrel and the shroud near the bolt and the bolt face.

For the conversion, I notice the locking lugs and the chamber throat starts gets a bit more dirtier than usual. Keep in mind the bullet must "freely fly" in the chamber, then lock into the bore groves. Basically for the first 60 mm, the .22lr is traveling without guidance until it reaches the throat of the chamber where it will track lightly on the grooves. I don't think it would cause damage or that much accuracy issue, but I do believe it makes for slightly more build up than normal. Perhaps a small .0001mm space between the throat and the bore. I believe as the bore's throat wears out more, the lead build up in that area will be greater. It can all be cleaned up by simply firing a 5.56mm round through it.