LGS has a CMMG .22 conv kit in stock with 3 mags for $179 an I was thinking of picking it up. I have a lot of .22 ammo laying around an was wondering what peoples experience with these have been.
Any .22 ammo to avoid?

Thanks

5.56 barrel twist is usually too fast to get good accuracy.  A dedicated 22LR upper is the way to go.  Also, I would stick to plated bullets as lead have lubes of varying types.

I have one - works great...
Accuracy is absolutely sufficient up to 100m. Didn't shoot paper but 100% hits on a 5" steel plate. I used it in my Modmat Wartime SBF (12" barrel)

Yep - valid point on the ammo - it all sucks and things get really dirty after shooting some 22lr

OP - mind sharing which LGS? I've been thinking about picking one up.  Was just looking at it on Midway, but they only have the 10 rd mags

I picked one up about a month ago, I paid roughly that price, but only 1 mag included.
Four different brands of .22lr through my 1/7 twist 11.5" pistol.
One FTF after about 10 rounds. Zero malfunctions the rest of the time.
Accuracy was acceptable at 30 yards, and it was a blast to shoot.
I need to find some time to run it some of my other AR platforms, curious
to see if any appreciable differences are apparent with different barrel lengths, twist rates and such.
The instruction manual included does advise to swap the 5.56 BCG back in and send a few rounds,
after using it with .22lr, supposed to help clear out deposits.
The conversion BCG itself is pretty cool in how it operates, though I feel like some of the welds are
just a tad subpar for my taste. I do like it, I'd advise you to buy it now, especially if you have a good amount of .22lr!

Mine has been fine but some have had issues

That being said, I would definitely buy another.

That's a great price, best I've seen is $199 free ship at righttobear.com (OOS, ATM). Primary Arms also has them for $199 + ship (in stock ATM). These are the kits w/3 24 rd. mags.