often, 2" x 16", with 6" of that length telescoped back around the barrel. It weighs at LEAST 1.5 lbs. Such a can IS capable of handling rapidfire with full charge 308 ammo. trouble is, it makes the rifle handle about like a 28" barreled 12 ga, with a mag extention that runs all the way out to the muzzle, full of buckshot. THAT is why 308 autorifle fans DONT use one. THAT is why a shorty 223 is a FAR better all around choice, for shtf (along with the .22lr conversion unit).