Anyone know if the barrel on any of the later AR-7 clones (Charter Arms, Survival Arms, AR-7 Industries, Henry Arms) will fit on an original Armalite AR-7? I've got an Armalite with a "compromised" barrel and am looking for a replacement. Until recently, Armalite listed AR-7 barrels as separately-available components ... but not anymore. I guess I'm really concerned primarily with a current producer (whoever that is) that would sell a barrel separately. Any suggestions? Thanks in advance.