To save a bunch of money, and get more trigger time which I think is always a good thing, consider installing one of the .22LR conversions in your AR-15. I have a CMMG .22 LR conversion (http://www.brownells.com/rifle-parts/bolt-parts/caliber-conversion-kits/ar-15-22-lr-conversion-kits-prod54549.aspx) in my 16” AR-15 upper and love it! The biggest challenge with a .22 conversion is getting the gun to “run”, which always comes back to the magazine and ammo being the key issues. The first problem is finding the ammo that both the magazine and your rifle like. I took the recommendation of the Brownells Tech Staff and bought Federal Champion 36 grain, high-velocity.
http://www.brownells.com/ammunition/rimfire-ammo/federal-premium-champion-high-velocity-rimfire-ammunition-prod43060.aspx?avs|Cartridge_1=AFF_22Long Rifle . I also took their advice and tried Black Dog magazines. Of the five I bought there were two that wouldn’t feed consistently so they are now doing a “time out” in the corner of my garage. I’ve also heard great things about another conversion magazine, with the link below, though I see it’s on back order like so many other rifle items: http://www.brownells.com/magazines/rifle-magazines/magazines/ar-15-m16-22-lr-magazines-prod27652.aspx
Accuracy using the .22 caliber conversion unit is as precise as I’m used to with my AR-15 but it’s not terrible. I was able to keep five shots in 1” at 25 yards using a non-magnified EOTech sight. That was good enough to earn me some kudos at a recent Zombie match, where I wasn’t the fastest competitor but I had a head shot on everything. (And that gives me a lot of satisfaction!)
The CMMG Kit has everything you need though you’ll want to order more magazines. A big plus is that the kit is easy to install; just remove the stock bolt and carrier, and slip in the conversion. One big caution is make sure the chamber and bore are clean BEFORE you install the conversion. When you take the conversion out clean the bore and chamber thoroughly. This attention to keeping things clean is a MUST as .22LR is kind of dirty. If you leave gunk in the chamber throat it could cause your centerfire rounds to jam. The other caution is Do Not believe folks who tell you “shooting a jacketed round through the bore will clean out the lead and lube fouling”. Bullets aren’t scrapers, they are tapered and will simply wedge the fouling deeper into the pores of the metal. Take the time and clean your gun thoroughly when switching back and forth.
Shooting an AR-15 with the .22LR conversion is a blast! There’s no recoil, noise is low and you can put a lot of rounds down range for very little money. Plus there’s no gunsmith needed for the conversion. The best part is you still have your AR15, centerfire rifle, when you want to shoot a 3-Gun match or some varmints.