The Schillelagh missile is fired by the M551 sheridan light weight tank. The HEAT missile has a 152mm diameter and a longitudinal key located just behind the warhead. The key fits into a slot in the gun tube and prevents the missile from rolling as it travels through the tube. The key also acts as a loading index to orient the missile gyros.. The rear cap contains the firing connections and is left in the breach during firing. After the missile leaves the barrel, the stabilizer fins spring into place.