If any of you have any experience with these rifles at ranges of 100yds to 1000yds please let me hear what your opinion is as far as their accuracy and aility to be used effectively in competition shooting. The AR being a Bushmaster DCM competition rifle .223 and the other two being very basic models in .308 that are currently going for around $400 to $800. Thanks for all your input.

Well at 100yds the AR-15 is going to win hands down.
At 300-600, still the AR-15 goes with the blue ribbon.
At 1000, a .308 surpasses the tiny .223 round competitively, even in the hands of an experienced shooter.

If you're only shooting 600-800 yard matches though, the Bushmaster will suit you admirably against any of the other rifles for a smaller price.

By the way, nobody turns an FAL or, perish the thought, a HK91/G3/Clone into a competition rifle.  The AR15 style rifles, however, are superior in both ironsight and scoped match types.