I found an AR at the gunshow this weekend for $600. Struck me as too good a deal to pass up but now I have to admit that I don't really know what I have. It's a very classic looking AR. Fixed stock, non removable carry handle w/adjustable ghost ring style sight. Front sight appears cone shaped and has <-UP markings. Appears to be a 20" barrel and is 'front heavy' IMO. The lower is marked CLOUD MT. ARMORY NEWBERG, OR CAL. MULTI MOD. CM1500 05-0053 How do I find out what kind of upper I have? Can I shoot 5.56 or should I stick with the .223? Anything else I should know?