One of the great mysteries of the modern AR-15 is the so-called Government profile barrel. The original AR-15, and M16, had the so-called “standard” profile. Today, we call this a “pencil” profile. When the design work for the M16A2 happened in the 80’s, the design team shifted away from the lightweight style. The thicker barrel at the muzzle became the new standard. Eventually, all modern enthusiasts ask why that happened.