Hey, I want to buy a gun that is basically the exact civilian version of the M-16A2, so I obviously looked to the AR-15.  However, I was caught off guard by just how many different models there are.  So, what I basically need to know is that if I wanted the civilian version of the M16A2, everything from same caliber to barrel length to inclusion of handguard, which model AR-15 do I want?

A carry handle model
with a 20 inch non h-bar barrel
with a chrome lined bore.