81mm Shell, M57
This article is from TM 9-1904 which is available on this site.
The contents have been supplemented with modern photos and comments or additional information added in some instances.
Date Compiled: 7/17/2007
Editor: Chris Guska
SHELL, Chemical, M57. This shell is used for the placing of smoke screens and gas clouds with a secondary incendiary effect when WP is used as its chemical filler.
Shell body. In general construction, this shell body has the same outer characteristics as the High-explosive Shell M56. The nose of the shell is threaded to receive the type of adapter peculiar to chemical shell. The adapter is threaded internally to receive the Point-detonating Fuse M52 which has a super quick action. All chemical shell to produce efficient dispersion of filler must burst above ground. A super quick action fuse is therefore used to produce such action. For details, in function of the M52 P.D., see pages 298 to 300.
The chemical filler is loaded into the shell body, and then the burster casing is pressed in place. The head of the Burster Casing M2 is wider than the body of the burster casing and has a slight taper; when pressed into place in the adapter sleeve it forms a gastight seal and acts as a seat for the burster charge. A recess is machined in the base of the shell body internally so as to receive the end of the casing, preventing it from becoming loose due to the shock and jars inc,.-dent to shipment . During the loading of the chemical filler and the pressing of the burster casing in place, there is no explosive charge present in the casing.
The Burster Charge M1 consists of tetryl pellets or tetrytol in a thin aluminum or cardboard cylinder. It is placed in the burster casing prior to the assembly of the fuse to the shell. This construction burster as compared to the old booster found in the 3-inch smoke shell is much more efficient. The explosive charge runs through the entire length of the shell and splits the shell from nose to tail upon function of the fuse, allowing for the dispersion of all the chemical filler in the shell. The old booster charge found in 3-inch smoke shell split the shell near the nose where the booster charge was located, and allowed a good deal of the chemical filler to remain in the base of the shell.
The fin assembly, ignition cartridge, propellant increments and percussion primer are identical to those used with the High-explosive Shell M56.
Three chemical fillers are loaded at the present time; WP smoke, FS smoke, and H-gas. The weight of the completely assembled round varies with the filler used. The weights of the various rounds are:
Filler
Weight of Filler
Weight of Completely Assembled Round
WP
4.04
11.50
FS
4.59
12.00
H
3.15
10.45
The total length of the shell with the fuse assembled is 22.89 inches.
Marking and packing. Shell loaded with WP and FS are painted a blue-gray base color with yellow stencil and one yellow band to indicate non-persistant screening smoke filler. Shells loaded with H are painted a blue-gray base color with green stencil and two green bands indicate persistent toxic filler.
Packing is the same as for M56 High-explosive Shell.
