4.5-inch H.E. M8, M8A1, M8A2, and M8A3;

also Practice M9, M9A1, M9A2, and M9A3

Over-all length, inches

Total weight, pounds

Head length, inches

Wall thickness, inch

Burster tube length, inches

Fin length, inches

Bursting charge (TNT), pounds

Maximum range, yards

Muzzle velocity, ft./sec.

Fuzing

M4, M4A1, M4A2

General: The initial issue of the rocket went to the Army Air Forces for projection from air-craft launchers against ground targets; but, in-asmuch as the rocket was origi-nally designed for use from ground launchers, its use in air-craft has been discontinued.

Construction: The head is a thin-walled high-capacity type, rounded at the nose to form the ogive, threaded at the nose to take the fuze adapter, and threaded externally aft to fit into the motor. A burster tube is fitted to the head and extends down into the motor, a design which utilizes the motor tube for additional fragments, since the burster tube as well as the head itself is loaded with TNT.

The motor is a steel tube of uniform diameter except at the after end, where it con-stricts and then flares to form the nozzle. The motor houses the trap assembly, which consists of ten wire running from the trap plate on the forward end to the trap ring on the after end. The trap assembly holds the thirty sticks of propellant and fits around the burster tube. The motor tube is threaded internally forward to take the head, and just abaft this thread is a groove which weakens the tube to provide a safety shear point, should the motor pressure become too great.

The fin assembly for the rocket opens and guides the rocket in flight only after the rocket has cleared the launcher. The fins of the assembly are held in place by the fin re-tainer, which is expelled by the blast of the escaping gas. After clearing the launcher, the fins snap to their outstretched position. There are six fins.

The M8A1 involved a change in the desing of the motor tube to strengthen it on the threaded end. The head of the M8 was used by machining new base threads. Tests on the M8A1 indicated that the base of the modified head was weak, and a new head was designed for use with the motor of the M8A1. This rocket, the M8A2, will supersede the M8 and M8A1. The M8A3 is a modification of the M8A2 made by the addition of a locking burr to each fin blade to assist in rigidly maintaining the fin in full open position during flight.

Propellant: The propellant consists of 30 sticks of ballistite. Each stick is five inches long and 7/8 inches in diameter with a ¼-inch axial hole. Three sticks are placed on each trap wire, and there is sufficient clearance between the sticks and the wire to allow bur-ning of the inner stick wall simultaneously with the burning of the outer wall. Two igniter-bag assemblies are bound on two opposite columns of the propellant. The bags assist the ignition of the propellant by catching the flame of the igniter and, in turn, igniting the upper propellant sticks.

Practice Rockets M9, M9A1, M9A2, M9A3: These rockets are similar in design and construction to the M8 series, lacking only the explosive charge and live fuze. The Fuze M4 and booster may be assembled and used in the M9 as a spotting charge.

Figure 118. 4.5-inch H.E. Rocket M8