>>Hi Duane...
I too have a Bushmaster AR...set up similar to the one Bill describes, except I am currently using a 1.5 - 5X by 20mm Leopold on top with high mount scope rings (still have original folding sights on it which are usable). I LOVE this gun...and with the leopold it is quite accurate out to at least 125 yards (max I've been able to shoot it at thus far). The trigger on this beast is hardly crisp...but I got used to it...besides which for $100 you can get a nice drop in match-type unit...which I have yet to do as I don't need it. Mine is a .223.
Now regarding the 9mm... You might want to consider a Beretta Storm Carbine, which you can get in 9mm, .40, or .45. I've heard you can buy separate uppers to allow you all three calibers, but I can't confirm this. What I can confirm...is that in 9mm I have never had so much fun...!...and at easily half the price of your average AR. I have used the open sights, Leoplod, as above, laser sights, and currently a halo sight - all with excellent results. Matter of fact...just using the supplied open sights I can regularly hit a 10" metal pie plate at 125 yards fast (vs rapid) fire. Regular = hits on nine out of 10 shots...over and over. The gun really shines at 75 yards and under.
One of the many cool things about this gun is that it uses mags from a Beretta 92/96/maybe others...so if you are like me with half a dozen 92 high cap (15-20 round) mags for your pistol - then you are good to go...! Check it out...! You won't be dissappointed...!...TW<<