Identification

a. General. Ammunition and ammunition components are completely identified by the painting and marking (including an ammunition lot number) which appears on all original packing containers and, when practicable, on the item itself.

Rocket Nozzle Insulation

i'NSULAT(NG TU8ING (PROTECTS STRIPPED -SNC Of BLUE LEAD)

(blue lead (hemove insulating /¡tu3in6 before con-nectimg . / (wire to contact swung) ' / ^contact riv3

.¡temperature ^limits

EJECTION PIN.

-olive dsa2 v.'itm marking IN yellow-

(contact ring is untainted)

A-ROCKET. HI, AT, 3.5-1 HCH. M28A2 (SHOWN RfAOY FOR LOADING-

SHORTING CUP AND SAFETY BAND REMOVED AND SLUE LEAD WITHDRAWN FROM EXPANSION CONIJ

green lead. (ground wire)

•SHORTING CLP

-blue wtk marking in white'-

(contact r'ng is un painted)

8-ROCKCT. PRACTICE, 3-54NCH, M29A2 (SHOWN AS REMOVED FROM PACKING-BLUE Li AD, SHORTING CUP, AND SAFETY BAND IN PLACE)

h. Modku To identify a particular design, a model designation is assigned at the time the design is classified as an adopted type. This model designation becomes an essential part of the itenvs standard nomenclature and is included in the marking on the item. The present system of designating the model ie to vise the latter "M" followed by an arabic numeral. Modifications are indicated by adding (lie letter "A" and the appropriate arabic numeral. Thus. "MlOOAl" would signify the first modification for ail item for which the original model designation was "MIOO."

C. Ammunition Lot Xcmrkr. At the time of manufacture, every item of ammunition is assigned a lot number in accordance with pertinent specifications. When practicable, this lot number is stamped on the item itself. In addition, an ammunition lot number is assigned to the complete rounds. The ammunition lot number is stamped or marked on each round and on all packing containers. It is required for all purposes of record, including reports on condition, functioning, and accidents in which the ammunition is involved. To provide for the most uniform functioning, fixed rounds of any one lot are made up of single lots of components whenever practicable. For the greatest uniformity in firing, successive rounds should be from the same ammunition lot.

d. Marking. Standard markings are stenciled on the rocket in the appropriate color (fig. 42 and e below). They include the type, size, and model of the item; the ammunition lot number which consists of the loader's initials or symbol, the loader's lot number, and the date (month and year) of loading; and the temperature limitations within which it is safe to fire the rocket.

e. Painting. Ammunition is painted to prevent rust and to provide, by the color, a means of identifying each type. Rockets are painted as follows :

HEAD:

HE, AT—Olive drab, marking in yellow. Practice—Blue, marking in white.

MOTOR: HE, AT and practice—Olive drab.

63. Care, Handling, and Preservation a. Ammunition is packed to withstand conditions ordinarily encountered in the field. Care must be observed to keep packings from being broken or damaged. All broken packings must be repaired immediately and careful attention given to the transfer of all markings from the old to the new parts. When it is necessary to leave ammunition in the open, raise it on dunnage at least 6 inches from the ground and cover it with a double thickness of tarpaulin, leaving enough space for circulation of air. Suitable trenches should be dug to prevent water from running under the pile.

}). Since explosives are adversely affected by moisture1 and high temperatures, due consideration should be given to the following:

(1) Bo not break the moisture-resistant seal until ammunition is to be used. Ammunition removed from an airtight container, particularly in warm damp climates, is subject to accelerated corrosion and deterioration, thereby causing the ammunition to become unserviceable.

(2) Protect the ammunition from sources of high temperature including the direct rays of the sun. Rockets should never be stored where the temperatures may exceed 120° F.

c. Rockets must not be disassembled.

d. Rockets should be protected from mud, sand, dirt, and water. If rounds become dirty or wet, they should be wiped off at once with a clean, dry, wiping cloth.

e. Explosive ammunition must be handled with appropriate care at all times. The explosive elements in igniters and fuzes are particularly sensitive to undue shock and high temperatures. Boxes containing ammv/nition should not be dropped, thrown, tumbled, or dragged.

/. In handling and storage, complete rounds should at all times be kept pointed in that direction which would result in the least damage should the propellent be accidentally ignited.

g. Rounds prepared for firing, but not fired, will be returned to their original condition and packings, and appropriately marked. Such ammunition will be used first in subsequent firings so that stocks of opened packages may be kept to a minimum.

h. Do not handle duds. Because their fuzes are armed, and hence extremely dangerous, duds will not be moved or touched, but will be destroyed in place in accordance with TM 9-1900.

64. Authorized Rounds a. General. Ammunition authorized for use in the 3.5-inch rocket launchers M20 and M20B1 is listed in table I. Standard nomenclature, used in the listing, completely identifies each item except for the lot number.

b. Rocket head.

(1) The HE, AT rocket head M28, M28A1, and M28A2, consists of a thin gage steel body cylindrical in shape and tapered at the rear—the cylindrical portion is 3.5 inches in diameter, the rear of the tapered portion, approximately 2 inches. The body contains a shaped charge of 1.93 pounds of COMP B held in place by a thin gage metal cone. The forward end of the body is closed by a thin gage metal ogive. The weight of the complete head is approximately 4.5 pounds.

(2) The practice rocket head M29, M29A1, and M29A2 consists of a hollow cast iron body of the same external dimensions as the HE, AT head. The forward end is closed by a thin gage metal ogive similar to that fitted to the HE, AT head. The weight of the complete head is approximately 4.65 pounds—the weight of the cast iron body compensating for the absence of a filler. An alternative head consists of the metal parts of the HE. AT rocket head and an inert filler to bring the weight up to that of cast iron practice head.

Table I.—Authorized ammunition

Standard nomenclature of complete round

Complete round

Rocket head

Rocket motor

Fuze

HE HE HE

None* None* None*

(lb)

Model of igniter

Model of propellent

Weight of propellent <M

Standard nomenclature

Action

ROCKET, practicc, 3.5-inch, M29 (T85E2).

ROCKET, practice, 3.5-inch, M29A1.

ROCKET, practice, 3.5-inch, M29A2.

23. 55 23. 55 23. 55 23. 55 23. 55 23. 55

8. 90 8. 00 8. 90 8. 90 8. 90 8. 90

COMP B

COMP B

COMP B

None'1' None* None*

1. 93 1. 93 1. 93

M 20

(T18) M20 (T18)

M 7 M 7 M 7 M7 M7 M 7

0. 36 . 36 . 36 . 36 . 36 . 36

FUZE, rocket, dummy, M405 (T2008E2).

FUZE, rocket, dummy, M405 (T2008E2).

FUZE, rocket, dummy, M405 (T2008E2).

Nondelay.

Nondelay.

Nondelay

Inert,

Inert,

Inert.

*Head consists of cast iron body with steel ogive and no filler. An alternative head consists of steel body and ogive, inert loaded to weight.

*Head consists of cast iron body with steel ogive and no filler. An alternative head consists of steel body and ogive, inert loaded to weight.

Motor assembly.

(1) Description. The rocket motor assembly consists of the propellent and igniter housed in a metal tube to which the iin assembly is securely attached. The front end of the tube is assembled to the base of the fuze—the rear end is constricted to form a nozzle. The cylindrical motor cavity is divided into four sections by two axial spacer plates set at right angles to each other. The rear ends of the spacer plates rest against the trap. The same motor is used for both the HE, AT, and practice rockets, although there are some differences in the motors assembled to rockets of different modifications. The principal differences are in the trap, fin, and contact ring assembly, as indicated below. The trap in the M28 and M29 rockets is a cast steel grid whereas that in the later modifications is a steel disk with drilled holes.

(2) Propellent. The propelling charge consists of 12 grains of the MT propellent. Each grain is 5 inches long and approximately % inch in diameter and weighs 0.03 pound. Three grains are placed in each of the four sections (a total of 12 grains—0.36 pound—of propellent) formed by the spacer plates. .. Each lot of propellent is adjusted at the time of manufacture to give standard velocity. Since the rate of burning increases with the initial temperature, it is important not to fire rockets at temperatures beyond the limits marked on each rocket. Firing at temperatures below the minimum ( — 20° F.) will give erratic ranges and excessive back blast of powder particles; firing at temperatures above the maximum ( +120° F.) will cause dangerous pressures to build up within the motor. The propellent is ignited by the igniter M20 ((3) below).

(3) Igniter and leads. The igniter M20 (T18), which consists of a short, cylindrical, plastic case containing a 3-gram black powder charge and SQUlB, electric, Ml, is assembled in the forward end of the motor on top of the propellent spacer plates. The leads of the electric squib, running parallel to the grains of propellent, pass from the igniter through the nozzle closure into the expansion cone ((4) below7). The green lead (ground wire) is connected to the support ring of the contact ring assembly ((4) below). The red lead (live wire) is connected to the contact ring by a tubular rivet which passes through but is insulated from the support ring. These connections are positioned 180° apart. The blue lead ("pigtail") is actually an extension of the live wire (fig. 42) and, as such, has one end connected to the same terminal as the red lead—i he free end being connected, at the time of loading, r.o one of the contact springs on the launcher contact, spring clamp. The blue lead is coiled and placed in the expansion cone during shipment—it is held in this position by a piece of adhesive tape. The free end of the pigtail is stripped and then covered with a piece of plastic tubing which insulates the stripped end during handling and shipping—this insulating tubing is removed just prior to connecting the blue lead to the contact spring.

(4) Fin assembly. The fin assembly for each model of rocket consists of an aluminum-alloy expansion cone, three pairs of aluminum-alloy fins (6 fins) and a contact ring assembly. The contact ring assembly, which encircles the fins, consists of three rings: Innermost is the aluminum support ring which is separated from the cadmium-plated copper contact ring (outer ring) by a laminated plastic insulating ring. The fins are spot welded to the expansion cone and the expansion cone is press-fitted to the rear end of the motor tube. On the M23A2 and M29A2 rockets (fig. 42) the contact ring assembly is 1.78 inches wide and the groove in the support ring for engagement with the latch mechanism of the launcher is to the rear of the contact ring, whereas for the other modifications the contact ring assembly is 1.04 inches wide and the groove is forward of the contact ring.

Inch M20 Fuze

RA PO 113366

(1) Description. This base-detonating fuze (figs. 42 and 43) is of (he simple inertia type which functions with nondelay action upon impact. The fuze body and safety band are olive drab; the fuze nomenclature, the loader's lot number, and the month and year of loading are stamped into the metal. An ejection pin, which passes through the fuze body and prevents movement of the internal parts, is provided to preclude accidental functioning during shipping, handling, and firing. An additional safety feature is provided by the safety baud which prevents the ejection pin from moving during shipping and handling. The safety band is not removed from the fuze until the rocket head has been loaded into the launcher. The fuze mechanism consists of a plunger, au actuating sleeve, a firing pin, a setback sleeve, a creep spring, a stop pin, and a lock pin. The explosive train includes a detonator and booster.

(2) Functioning. When the safety band is removed, the ejection pin moves outward approximately % inch but still prevents all parts of the fuze mechanism from moving. When the rocket is fully seated, the ejection pin is partially depressed by the launcher thereby freeing the setback sleeve so that it can move on setback. It should be noted that in this condition the fuze is still safe since the ejection pin prevents movement of the actuating sleeve and firing pin. If it becomes necessary to remove the rocket from the launcher, the ejection pin will move outward and reengage the setback sleeve thus returning the fuze to its original safe condition. When the rocket is fired, the force of setback opposing the action of the creep spring moves the setback sleeve to its rearward position where it is held by the lock pin. When the rocket leaves the muzzle of the launcher the ejection pin is thrown clear of the fuze, and the fuze is fully armed. During flight, the firing pin spring prevents the firing pin from striking the detonator, and the creep spring retards forward movement of the plunger and actuating sleeve. The action of the creep spring is strong enough to retard the plunger and actuating sleeve and to prevent the fuze from firing should the rocket strike a light object such as light brush or undergrowth. Upon impact with a more resistant object the plunger and actuating sleeve move forward—the sleeve hits the firing pin lever causing the firing pin to strike the detonator and explode the rocket.

c. Fu/.k. Rockkt, Dummy, M405 (T200SE2). The M40o, used for practice purposes, is an inert fuze which incorporates an ejection pin assembly simulating that used in the BD fuze M404 (T160E6) (d above). The body of the fuze and the safety band are painted blue. The fuze nomenclature, the loader's lot number, and the month and year of loading are stamped into the metal.

65. Preparation for Firing a. After the rocket is removed from its packing, the rocket is prepared for firing as follows:

(1) Remove the shorting clip (fig. 42) from the contact ring assembly before loading rocket into launcher.

(2) Insert rocket head into launcher, then remove the safety band from fuze.

(3) Seat rocket fully so that latch engages the notch in the fins.

(4) With the launcher set at SAFE, the blue lead is withdrawn from the expansion cone, uncoiled, and the insulating tubing removed from the stripped end.

(5) Connect stripped end of wire to one of the two contact springs on the launcher, whichever is the more convenient, b. For rockets prepared for firing but not fired, the launcher will be unloaded as follows:

(1) Set the launcher at SAFE.

(2) Disconnect blue lead from contact spring.

' (3) Insulate the stripped end of blue lead, coil the lead and replace it in the expansion cone. Tape the blue lead to the expansion cone.

(4) Disengage the latch from the groove in the support ring and carefully withdraw the rocket from the launcher until the fuze is exposed.

(5) Replace the shorting clip on contact ring assembly.

(6) Replace safety band on fuze.

(7) Remove rocket from launcher.

(8) Restore rocket to its original condition and packing.

66. Precautions in Firing

The following will be observed in order to prevent injury to personnel and damage to materiel:

a. If a rocket fails to fire and examination shows the launcher is not at fault, the safety band and shorting clip will be replaced and the rocket set aside for destruction by qualified personnel.

b. In firing rockets, consideration should be given to the blast of flame to the rear. Ammunition and personnel should be kept out of the blast area (par. 22a). The loader should exercise particular care to stand clear of the blast.

c. Do not fire rockets at temperatures below — 20° F or above + 120° F which are specified as the safe limits for each round (par. 04c (2)).

d. Rockets with damaged fins should not be fired since they are unstable in flight, hence erratic in range and deflection. Be careful when loading rockets into the launcher to prevent damage to blades of the fin assembly.

e. When firing front wooded areas or other cover, exercise care to prevent the rocket from striking branches or other objects which might deflect the rocket or even cause accidental functioning.

67. Packing

Rockets of this caliber are packed in individual, hermetically sealed, metal containers which, in turn, are packed in wooden boxes (fig. 44) in quantities of three containers (three. rockets) per .box. The exterior of the metal containers are painted to indicate t he type of ■rocket contained, that is, olive drab with yellow marking for the HE, AT rockets and blue with white marking for the practice rockets. The marking on the container includes an AIC symbol, nomenclature of the packed item, and ammunition lot number. The over-all dimensions of the packing box are approximately 20% inches long, 14% inches w7ide and 6% inches high. The total weight is 53 pounds and its displacement is 1.59 cubic feet. For more complete packing and shipping data see Department of the Army Supply Catalog ORD 3 SNL S-9 (now published as ORD f 1 SNL S-9).

IN ADDITION TO THE MARKING SHOWN. THE CLEATS OF BOXES CONTAINING PRACTICE AMMUNITION ARE PAINTED BLUE AND A BLUE STRIPE, 3 INCHES WIDE, IS PAINTED AROUND THE CENTER OF THE BOX IN THE POSITION INDICATED BY BROKEN LINES

RAPD 113353A

RAPD 113353A

Arabic Ammunition Box

SEE NOTE

Figure J/4. Packing box for 8.5-inch rockets.

SEE NOTE

A—lot number B—a1c symbol c—icc shipping name d—bursting charge E—nomenclature of packed item F—month and year loaded g—cubical displacement H—total weight

. ("nose end"—indicates position ©f rockets within box

Figure J/4. Packing box for 8.5-inch rockets.

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