Just get a Ruger 10/22T
With proper ammo and cleaning, it will reliably hold penny-sized groups at 100m.
My particular 10/22T likes Federal AutoMatch (Tan box, $15 for 1250 rounds), and Lapua Match (when I can get it)
A good .22 is an excellent training tool. The skills you learn at 100m with a .22, will carry you out to 600m with a larger caliber centerfire rifle. Windage, bullet drop, trigger pull, barrel cleanliness, flinch, sight picture, etc.

Note: Image isn't my rifle, but one that looks almost exactly like it
It's a Ruger .22, semi-auto, 10 round magazine. It's arguably THE most common semi-auto .22 in America.
The "10/22 Target" comes with a heavy target barrel, custom trigger, adjustable stock (Fajen), and no iron sights (need a scope)
You really really don't want to screw with an AR-15 with a subcaliber device. We had those nightmare devices in the Army, for the indoor ranges. They sucked. Badly.
I
think mine was about $400 for the rifle (w/ custom stock, trigger, barrel included from factory). Add $50 for a .22 level scope, or $150 for a proper Nikon or Leupold 10x scope. Add another $25-$50 for scope rings to mount the scope to the rifle. Have someone that truly knows what they're doing assemble the package -
and teach you how to shoot properly
Last edited by rdx-fx (2008-11-09 14:51:41)