time allows the M107 to practice shoot-and-scoot, redeploying before the firing position can be zeroed in on. One drawback of the M107 in combat was that laying the gun involves skilled minute movements of the entire vehicle. The gunner uses hand signals to the driver, who views them in the left rear view mirror and moves the vehicle left or right by tapping on the steering bar. The other cannoneers (aka "Gun Bunnies") set the collimator and aiming stakes under the direction of the gunner. Only two rounds are carried with its gun tractor on "loading trays". These rounds can be fired by the onboard crew of five (Section chief, driver, gunner, assistant gunner, Number one cannoneer) out of a total crew of thirteen. The rest of the ammunition and crew follow in the M548 Ammunition Carrier. If the gun was facing hostile artillery, the gun would fire and relocate where these crewmen would reload the M107 at the new location to avoid enemy counter-battery fire. Each member of the M107 crew has specific duties when the vehicle is firing. The Section chief operates the hydraulic load and ram, verification with "Gunner's Quadrant", as well as operating the rear spade and left spade unlock. The driver operates the positions spade and the barrel travel lock. The gunner controls deflection (the horizontal direction in which the gun is pointing). The Assistant gunner controls elevation. The Number one cannoneer opens and closes the breech, verifies ramming of the round with ram rod and powder load red on the rag (which means he can see the red igniter patch to verify that the powder is not put in backwards), loads the primer, hooks up the lanyard (pig tail), pulls lanyard on command, and unlocks the right spade lock. Cannoneers two through nine set up the collimator (US Army Tm 9-2300-216-10), aiming stakes, bore sight (For Direct Fire missions only), communications, prepare additional ammunition (including fuzing) and powder zones, provide security, drive the M548, operate the ring-mounted M2 .50 caliber machine gun, set up camouflage nets, dig a burn pit, and conduct the resupply of ammunition. Early barrels were limited to 300 firings with the maximum zone 3 propellant, but later examples extended this to between 700 and 1,200 firings with extensive bore scoping by the supporting U.S. Army Ordnance Company. Retubing the barrel was necessary when the barrel had exhausted its service life,