I recently bought an ar from the classified ads.  It has a bushmaster lower marked mod. xm15-e2s.  It has an upper in .45 that is not marked, and it came with 3 modified mags.  1uzi, 2 that i was told are grease gun mags.  Any info on what I bought would be appreciated and I paid 600 for it.  Good deal or no?  

Sounds like you have an Olympic Arms upper (Or possibly Dalphon upper, but unlikely) with a Bushmaster lower, an Uzi mag, and two Dalphon modified Grease Gun Mags.  $600 is pretty good, as a new .45 cal Olympic Arms upper will run $550-600.  You got the lower and two spare mags fro that price- good work!

The one way to be sure it is an Olympic Upper is take off the upper receiver, flip it over, and look to see if there is a post with a spring around it spanning across the opening in the reciever.  That is the ejector, and it is used only on the Olymipc Arms pistol caliber uppers.

Quoted: Sounds like you have an Olympic Arms upper (Or possibly Dalphon upper, but unlikely) with a Bushmaster lower, an Uzi mag, and two Dalphon modified Grease Gun Mags.  $600 is pretty good, as a new .45 cal Olympic Arms upper will run $550-600.  You got the lower and two spare mags fro that price- good work! The one way to be sure it is an Olympic Upper is take off the upper receiver, flip it over, and look to see if there is a post with a spring around it spanning across the opening in the reciever.  That is the ejector, and it is used only on the Olymipc Arms pistol caliber uppers.

Dead on, and a good price for the setup.   Finding more mags however will be a beotch, if you feel the need for more you'll likely be drawn to the Cavalry arms lower with hahn mag block.   It allows you to use unmodified greasegun mags which you can find for $5-15each.    Have fun and enjoy your rifle, the pistol caliber and particularly .45acp is a blast.  

Dawg, Mr.45, thanks for your replies.  It is an Olympic upper ( has the post/spring ejector).  I thought it was a good deal but wasn't sure.  My next task is to find a .223 upper for it.