18" is generally considered an ideal length, standard gas system (not the shorty) is preferred. Excellent rifle for a 1-4x or 1-6x scope (I like the ARMS mount for weight and size, but the DSA mount is bombproof). Dial in your gas, and it's reliable. slimmer dimensions make it more comfortable to carry and shoot than many other full-power rifles. Oh, and OVERPOWERED???? the 308Win/ 7.62x51mm is an excellent all-around cartridge. With the above setup, it is LETHAL out to 600 yards. Not "hit the paper", but rather "kill the deer". I have two... one is the above setup launching 175gr BTHP, the other is a 16" carbine loaded with Mk. 319 and an OEG on top. Slightly shorter and close to the same weight as an AR carbine with extended stock. May not be a "cool-guy" gun anymore, but I trust it a helluva lot more than my ARs when bad things happen.