Every so often, I resurrect an old post of mine.
The AR-15 is a wonderfully simple and modular weapon. You really ought to build one yourself.
First, get a Marine Corp technical manual for the M-16 for about $6, from Brownell's. Read that and also read the info on ar15.com. They have detailed instructions, too. Then get some tools--Screwdrivers, torque wrench. You might also need to get a military surplus AR-15/M-16 wrench tool for a few more bucks.
I got a stripped lower receiver from someone at ar15.com for about $100. It was made by PWA--"Pacific West Arms" of Milan, Illinois. A little birdie tells me that it is the same company that makes receivers for the folks at Wilson Combat. Lowers are available from Bushmaster, ASA, Olympic Arms, and lots of other sources. Shop around and get one transferred to you through your FFL.
I then got a 16" A2 carbine kit from
J & T Distributing . They are a very helpful and pleasant company to deal with. The current price for what I got is $440. The kit is manufactured by some military contractor, reportedly FN, and includes everything to turn the lower into a complete gun. The barrel is already correctly installed on the upper receiver and correctly headspaced. Many kits are available--20", bull-barreled, flattop, as well as genuine Colt M-4 kits.
I then spent an enjoyable afternoon putting my rifle together. You also need to get some magazines, a sling, and perhaps a front sight adjustment tool.
Cost: $6 + $100 + $440 + FFL fees + magazines + accessories + some of your time == Much cheaper than buying one already made. Of course you would have no customer service for the entire gun, but you probably won't need it. The J&T Distributing parts are top-notch and their customer service has been great. After putting the thing together, you would probably have the know-how to service it yourself if the need arose.
Of course, if you start tacking on all sorts of accessories such as optics, flashlights, accessory rails, lasers, and so forth, the cost would go way up. The only accessory I used was the plastic Ergo-Grip because it is much more comfortable than the standard grip.
My completed gun has never malfunctioned and is very accurate.