I have an Armalite AR10 a4 and love the gun. Well I love everything but the weight. Im ditching the prs stock and moving to something lighter. My dilemma is the 20" barrel with welded fsc brake. Id like to go carbine length while maintaining the slightly thicker barrel profile. Can the 20" be chopped to 16" and still run reliably with rifle length gas system? I've looked into having the gas port moved but it appears the barrel profile wouldn't allow it.