Description
The Mk IIIA is used in the Mk series HE shell for both 155mm gun and howitzer. It is made up of an adapter, a booster casing, and a fuze socket. The booster casing is threaded into the lower part of the adapter and contains a charge of either 1 ounce of tetryl or 0.50 ounce of tetryl and 0.50 ounce of TNT, the tetryl being placed around the fuze socket. The fuze socket is press-fit into the booster casing and is of a shape to receive the M46 Fuze. The adapter is threaded internally at the top to take the external threads of the M46 Fuze.
The M1 modification of the Mk IIIA consisted of beveling the inside shoulder at the top of the adapter so that the Mk Ill Fuze would screw in entirely. (The Mk III Fuze was replaced by the M46.) The interruptor of the Mk III Fuze was situated so as to contact the shoulder of the Mk. IIIA Adapter before the fuze was screwed all the way in.
The only difference between Adapter Boosters Mk. IIIAM1 and Mk. IIIAM2 is that the shoulder of the Mk. IIIA Adapter was beveled in the field to become Mk. IIIAM1 while the manufacture of the Mk. IIIAM2 included the beveled shoulder.
Functioning
No information about functioning.
See Also
Source(s)
TM 9-1904, Ammunition Inspection Guide (1944)
