If I'm just looking for something cheaper to shoot, on ocasion, than .223, do I really need a dedicated .22 upper?  Or can I just drop in my Ciener conversion and go?  I wouldn't be using the conversion to compete in any benchrest compitition, but only as a cheap alternative, and still be able to use my AR.

Thanks!

Standard .22LR bullets stabilize best when fired from a 1-in-16" twist barrel. If you want to use a .223 barrel, the best you can hope for is a 1-in-12" twist like what was used on the Colt SP1 rifles.

build another rifle!

Quoted: Standard .22LR bullets stabilize best when fired from a 1-in-16" twist barrel. If you want to use a .223 barrel, the best you can hope for is a 1-in-12" twist like what was used on the Colt SP1 rifles.

+1

Not to mention the fact that a .22 rimfire bullet is a couple of thousands of an inch smaller in diameter when compared to a .224" centerfire rifle bullet.  As you can imagine, that will do accuracy no good at all.

If you want a practice rifle for service rifle matches or some other percision dedicated task you are only going to be happy with a dedicated upper.
Most anything else-I think you will be a happy camper with the Ceiner unit.
I can throw my well broke in unit in any of three 1/9 bushy factory uppers and with a RRNM trigger,decent scope ,sandbag rest,and  standard velocity match ammo I am shooting better groups than my Ruger 10/22 Target. I am getting under 1" at 50 yd for 10 shot groups with Wolf ammo. High velocity and bulk ammo are 2 to 3" at the same 50 yards
You can use any and all AR toys you already have and the Ceiner Mags are a cinch to keep clean (very importaint with a dirty blowback .22) and come in both 10 round and 30 round.
Yes the bore is the wrong size and twist, but if you play around with different ammo it doesn't seem to care

I think if it were me, i'd spend the money on a 10/22 than on a .22 conversion.  I prefer having more guns than just more stuff for a few guns.