American Projectiles and Explosives
Army Rockets
2.36-inch A/T
Service: M6A1, M6A3, M6A4, M6A5
Practice: M7A1, M7A3, M7A4, M7A6
M6A1 and M6A3 Data
Total weight: M6A1 - 3.4 pounds; M6A3 - 19.4 pounds
Head length: 8.6 inches
Body length: 4.11 inches
Body diameter: 2.23 inches
Body wall thickness: 0.087 inches
Ogive length:
-M6A3 (Cone-Shaped): 4.5 inches
-M6A3 (Hemispherical): 4.56 inches
Ogive diameter (at flange): 2.245 inches
Motor tube length: 6.32 inches
Motor tube (inner diameter): 1.06 inches
Motor tube wall thickness: 0.095 inches
Maximum range: 700 yards
Effective range: 300 yards
Muzzle velocity: 265 feet/sec
Color: Olive drab
Explosive: Pentolite
General: Pill boxes, tanks, and armored vehicles are prime targets. The rocket can also be used in a stationary emplacement for demolition or as an anti-tank mine or a booby trap. The rocket can penetrate three inches of homogeneous steel armor plate at all ranges and at angles of impact as low as 30 degrees, employing the shaped-charge explosive.
Launcher: The Rocket Launcher M1A1, commonly called the "bazooka", is an electrically operated weapon of the open-tube type, fired from the shoulder, and weighing 13.26 pounds. Rocket Launcher M9A1 is similar but breaks down into two sections, each 31 inches long, for ease in transporting.
Construction: The 2.36-inch A/T Rockets M6A1 and M6A3 are identical except for difference in the ogive and the tail assembly. In other respects the two rockets are similar, consisting of a hollow ogive crimped onto the body, a body union fitting into the base of the body with internal threads to receive the motor, and a fuze which is located in the forward end of the motor tube. The M6A1 has a conical ogive, whereas the M6A3 has a hemispherical ogive which gives better penetration by forming a stronger stand-off piece for the shaped-charged effect of the explosive. M6A4 is like the M6A3, except that it is lighter, being made of high-strength alloys, and also uses the Bore-Safe Fuze M400. The M6A5 uses the Bore-Safe Fuze M401 and has a larger propellant grain, which eliminates the safety disk.
Tail Assembly: The M6A1 has six fins (5 and 1/2 inches long) spot-welded to the nozzle, a steel cup internally threaded at the forward end to screw onto the motor tube. The M6A3 has a different type of tail assembly to obtain fin area and counteract the change of the center of gravity effected by the hemispherical nose. This tail assembly consists of four sheet-steel fins 2 and 5/16 inches long, each of which is curved over an arc of 90 degrees on its outboard edge to form a blade. Each fin is joined to the other by welding, with an overlap of approximately a 1/2 inch to form a circular drum which is actually nothing more than a continuation of the four fins. The bases of the fins are spot-welded to the nozzle. In the M6A5 and M7A6 the free end of the ignition wire is attached to the shroud tail by a chip-board disk, instead of the tape on earlier models.
Propellant: The propellant consists of five sticks of ballistite. On an average, the propellant weighs approximately 61 and 1/2 grams, though it is loaded not by weight but rather by length of powder stick, to keep the pressure for various rounds at a relatively constant value. The M6A4 and M6A5 use the Powder M7, which burns at a lower temperature, +120 to -40 degrees Fahrenheit.
Fuze: The fuze for the M6A1 and M6A3 consists of a steel firing pin which slips into the central cavity of the fuze body, where it is held in a rearward position by the firing pin spring. A circumferential groove midway down the length of the firing pin receives the safety pin, which extends through the motor tube. When the safety pin is removed, the firing pin is free to move forward, restrained only by the action of the firing pin spring. After the safety pin has been removed, the firing pin will overcome the spring and detonate the rocket if it is dropped over four feet. The fuze body contains the Detonator M18 of lead azide and tetryl, and the booster charge of tetryl.
Remarks: The practice rounds are similar to their accompanying service rounds, except that they are inert-loaded and have a dummy fuze or steel weight to fill the empty fuze space.
The M6A5 and M7A6 have plastic closing plugs, making them waterproof rounds. They also use the Powder M7, which burns at a lower temperature, +120 to -40 degrees Faherenheit.
The M6A1 and M7A1 are now considered obsolete.
2.36-inch Smoke (W.P.) M10, M10A1, M10A2, M10A3
M10 Data
Total weight: 3.4 pounds
Head length: 5 and 1/2 inches
Head diameter: 2.3 inches
Maximum diameter: 2.36 inches
W.P. charge: 405 grams
Burster charge: 4 grams
Effective range: 300 yards
Color:
-Motor: Olive drab
-Head: Blue grey
General: This rocket is designed not only as a screening agent, but also to cause casualties. White phosphorus in smoke form has little effect upon the human body, but particles cause small burns. This rocket makes an effective weapon for dislodging enemy troops from dug-outs and foxholes.
Launcher: The 2.36-inch Smoke Rocket M10 is fired from the Launcher M1A1 or M9, the "bazooka".
Construction: The components of this rocket are the motor and the head assembly. The motor presently used is the M6A1, which is being replaced by the M6A3. As new motors are developed, it is contemplated that this rocket will be modified.
The head assembly consists of a container for the smoke charge with a long burster well containing PETN inserted from its after end. A collar is soldered to the base of the container. The spacer slips over the threads of the collar and is held against the flat surfaces of the collar by the fuze body, forming a joint between the two. The primer holder is threaded into the fuze body.
Tail Assembly: The 2.36-inch Smoke Rocket M10 has the standard tail assembly for this M6A1 or M6A3 motors.
Fuze: The fuze is similar to that used in the A/T Rocket M6A3.
Remarks: The M10A1 and M10A2 differ from the M10 in the type of propellant used. The M10A1 used the T1E1 Salted Powder, with a temperature range of 120 to -20 degrees Fahrenheit. The M10A2 uses the Powder M7, 120 to -40 degrees Fahrenheit. The M10A3 differs from the M10A2 in that it uses the Fuze M401.
3.25-inch Target M2, M2A1, M2A2
Width across fins: 24 inches
Weight: 37.5 pounds
Propellant weight: 3.2 inches
Range: 1,700 yards
Maximum velocity: 530 feet/sec
Burning time of flare: 30 seconds
General: This is a high-speed target for firing practice with automatic A.A. weapons.
Propellant: The propellant has grains five inches long and 7/8-inch in diameter, with a 5/16-inch axial hole. It is ignited by an electric squib.
M2A1: When a flare is added to the 3.25-inch Target Rocket M2 for anti-aircraft target practice at night, the resulting projectile is designated as the M2A1. The flare burns for 30 seconds from the beginning of flight.
M2A2: This design has a flat nose, to which is threaded a yellow flare for both day and night tracking. It also has a different system for igniter contact: the lead wires pass in turn through the nozzle and an inner fiber closing cup and connect to a household-type service plug, which is held by an outer fiber-board closing cup. There are 18 inches of igniter cable coiled between the closing cups, to allow ample lead for connecting to the launcher.
4.5-inch H.E. M8, M8A1, M8A2, and M8A3; also Practice M9, M9A1, M9A2, and M9A3
Total weight: 38 pounds
Head length: 7.5 inches
Wall thickness: 0.2 inches
Burster tube length: 15.5 inches
Fin length: 4 and 1/3 inches
Bursting charge weight (TNT): 4.3 pounds
Maximum range: 4,500 yards
Muzzle velocity: 840 feet/sec
Fuzing: M4, M4A1, M4A2
General: The initial issue of the rocket went to the Army Air Forces for projection from aircraft launchers against ground targets; but, in-asmuch as the rocket was originally designed for use from ground launchers, its use in aircraft 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 constricts and then flares to form the nozzle. The motor houses the trap assembly, which consists of ten wires 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 retainer, 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 design 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 suspersede 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-inch in diameter with a 1/4-inch axial hole. Three sticks are placed on each trap wire, and there is sufficient clearance between the sticks and the wire to allow burning 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.
4.5-inch H.E. S.S. M16, M16E1, and M16E2; Practice M17, M17E1, and M17E2; M20 and M21
M16 Data
Total weight: 42.5 pounds
Head length (w/ burster tube): 23.29 inches
TNT charge: 4.3 pounds
Maximum range: 5,250 yards
Muzzle velocity: 830 feet/sec
Fuzing: M81
Description: The head, loaded with high explosive, contains a fuze-well cup and a burster tube. The burster tube projects about 15 inches into the center of the rocket motor to secure additional fragmentation. The motor body is a steel tube threaded at each end to receive the head and the nozzle plate, which contains eight nozzles equally spaced in a circle and one nozzle in the center. The eight nozzles are set at an angle in order to impart rotation to the round when fired. The center nozzle is normally closed by a blowout disc which is designed to fail when the internal pressure in the body surpasses a predetermined limit. The nozzle openings are protected by a plastic sealing disc which remains in place during firing and is blown out by the rocket blast.
Propellant: The propelling charge consists of 30 grains of ballistite strung on wires of a cage-like trap. The igniter consists of a charge of black powder enclosed in a plastic tube attached to the trap and running the length of the charge. The tube also contains an electric squib. The leads of the squib pass through one of the nozzles, one lead being ground to the motor body and the other connected to a contact ring.
M20: The M20 is similar in design and construction to the M16, differing only in that the ignition wires are attached to spools rather than contact rings.
Practice Rockets M17 and M21: These are similar in design and construction to the H.E. rounds, but lack the explosive charge and the live fuze.
The M16E1 has a deeper fuze cavity for the V.T. Fuze M402 (Mk 173). Shipped with these rockets is a supplementary charge to fill part of this cavity in case the Fuzes M81 or M48A2 are used.
The M16E2 is like the M16E1, except that purge pellets of 411E composition have been added to eliminate chunks in burning.
5-inch A.R.
No picture available
The Army is currently using the Navy-designed 5-inch aircraft rockets.
7.2-inch Chemical M25 and M27
No picture available
Next Time: Army Developmental Types
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