Lets tak about AR15-22 conversion kits.
 

Having just bought my new PSA AR15, now I'm looking at buying a conversion kit to shoot 22's. What I had seen before was a full upper with a dedicated .22 barrel ($400-500). Now I just found where you can swap out the bolt carrier group and shoot .22's (~$150).

Obviously the .22 is smaller than the .223, but doesn't the bullet need to fit the barrel properly?

EDIT: Where's everyone buying their .223 ammo? Seems everyone is out of stock of it and mags.

EDIT #2: Let's keep it out of PARF please.

EDIT #3: Just ordered a .22 conversion from PSA!

BCG only:
CMMG ARC-22 .22LR Conversion Kits | Bass Pro Shops

Full upper:
Cabela's: CMMG 22 LR AR-15 Upper

If you want any sort of decent accuracy then get the dedicated upper as the 22LR upper/barrels have the twist for 22LR. The barrel twist on .223/5.56 is way off and the gun will probably shoot like a shotgun! If you just want to shoot it and accuracy is not a concern then the replacement bolt is the way to go.

You can't get .223 anywhere right now. You have to be lucky enough to be at the store when the shipment arrives. For the last few years, I've bought whatever big box was on Black Friday special.

I ordered a box of 800 from Cabela's, but it's on backorder for a couple of weeks. Should have bought a few extra mags and ammo earlier, but didn't know I was really going to get it until I did.

Every store and on-line store is out, unless you want to pay crazy, stupid money for it.

Tactical Solutions makes some top notch .22 uppers.

Tactical Solutions | High Performance Upgrades

I should have mentioned earlier, I have a Spikes Tactical ST-22 with their "fake" suppressor which can be changed to real but of course I would never do that! It can be changed to a regular AR-15 with an upper swap as the trigger group and hammer is the same as the .223 model.

For the money, I ask WHY? I'd rather spend the money on tricking out a 10/22 or buy the little Colt AR-15 .22 lookalike (built by Walther)

S&W makes an AR looking 22 that is reliable and priced well. I've used a number of conversion kits for this application and none of them have been as reliable as the Smith. The problems stem from the conversion from a gas operated system to the .22 cal kit which is spring operated. The springs can be a pain, (failure to feed, & or eject). I've even experienced a number of them that had issues consistantly going fully into battery (the bolt would stop about a 1/16 of and inch from full battery). I did like rouxroux suggested and tricked out a 10/22. AL

That was exactly my thought when I started looking at .22 conversions. Why buy a conversion when you can just get an entire .22?

I've got a spare lower, so I'm going to build one with a complete upper I just bought. Just need to determine what I need next and best deal.

With the upcomming bans rimfire might become HUGE! 22WMR. And 5mm remmington might gain some market share

Up until a couple of weeks ago, the best "conversion" was probably het S&W MP15-22. Get a whole new gun and be done....

Now however, I say "whatever you can get"
....