I have found that ammo is more of a factor for accuracy than the rifle. A lot of commercial ammo is lucky if it gets under 2" groups in any rifle. On the other hand, quality ammo or handloads can easily get to 1" or below in a run of the mill barrel.
I use a $395 (in 2010, including BCG!) PSA/FN 20" upper for sighting in my handloads. I get several loads that are 3/4" - 7/8" 5-shot groups at 100 yds. Honestly, I don't think I myself am capable of much better than that and it far exceeds my expectations for a milspec, chrome lined barrel that is not intended for match grade accuracy. I would love to see what a real target rifle could do with these loads but not enough to pay for one!
If you buy a name brand rifle, work on your shooting skills and use quality ammo you should have good accuracy without having to buy a target grade rifle. The AR15 platform seems to be fairly accurate. I think you would have to have a messed up barrel to shoot poorly, or bad technique.
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