I have a 20" A2 and wish to put a scope on it.  I have looked in the Bushmaster catalog and some other places and it seems that for the military type ARMS mount they want $50+.  That seems a bit high, but at some auctions they have what looks (and I mean exactly) like the $50 mount for $20 and call it a delta mount.  If they are all made of aluminum what is the deal?  What scope mount do you use?

The big deal is in the quality of the mount (is it REALLY to spec? Is it made of aircraft-quality aluminum?). The $50 you pay for the ARMS mount buys some of the the best quality that may be found. I used a Leatherwood mount, which was nice and tight (REALLY tight), but was much larger.