OP 1664 - U.S. Explosive Ordnance (Vol. 1); Part 1 - Projectiles, Propellants, and Projectile Fuzes; Chapter 1 - Projectiles; Section 15 - 7.2-inch Projectile: 7.2-inch Projector Charge "Hedgehog"

U.S. EXPLOSIVE ORDNANCE

PART 1 - PROJECTILES, PROPELLANT,
AND PROECTILE FUZES

Chapter 1 - Projectiles

Section 15 - 7.2-INCH PROJECTILES

7.2-inch Projector Charge "Hedgehog"

Over-all length, inches	38.6
Head length, inches	19.0
Head diameter, inches	7.2
Head weight, pounds	17.9
TNT filler, pounds	31.1
Wall thickness, inch	0.2
Tail tube diameter, inches	1.75
Tail width, inches	7.0

General: The projectile consists of a flat-nosed head with a conical tail fairing and parallel sides. The adapter and fuze thread into the nose. The motor unit consists of a smokeless powder cartridge with primer, which is lodged forward in the tail tube, the tube fitting over a firing post. The primer is detonated by electric contacts in the post. This charge is for use on Projector Mk 10 and Mk 11.

The tail is a steel tube attached to the head by a threaded joint. Tail fins have a 10-degree twist and are attached with a drum support to give a slow rotation and stabilized trajectory.

Remarks: When Torpex is used, the weight is increased by approximately 2.5 pounds.

The Above data are based on the 7.2-inch Head Mk 4A and the 1.75-inch P.C. Tail Mk 4A. These are being replaced by the 7.2-inch Head Mk 4 Mod 0 and the 1.75-inch P.C. Tail Mk 6 Mod 0.

Nose Fuzes Mk 136 and Mk 140 are replaced by the Nose Fuze Mk 158.