Construction: This fuze is threaded externally on the forward end to fit the large explo-sive gaine and externally on the after end to fit into the base-fuze carrier. Both the gaine and the base-fuze carrier are secured to the fuze by a grub screw. The fuze is bo-red in two diameters longitudinally. The after and larger diameter accommodates the arming mechanism and the head of the striker; the forward diameter forms a friction fit with the main body of the striker. The arming mechanism is housed in a metal block (fuze base) which threads into the after end of the fuze and is secured by a lock bolt. On the forward end of this block is an arming cam carrier supporting five interlocking arming cams, pivoted separately, which, in the unarmed position, rest in a circumferential groo-ve in the striker and hold the striker from the primer. A set-back plunger rests in a recess in the fuze base and is suppor-ted by the fingers of a metal sleeve. The forward end of the set-back plunger protrudes through the arming-cam carrier to prevent the movement of the master arming cam with which the remaining arming cams interlock. A safetypin holds the set-back plunger in the forward position before the fuze is installed into the projectile.

The gaine contains the primer, delay train, and booster. A thin cardboard disk is placed over the primer to prevent the striker from prematurely piercing the primer as a result of creep.

Operation: On set-back the set-back plunger moves back and is held by the fingers of a metal sleeve. The arming cams move out with centrifugal force, freeing the striker to move down onto the primer on impact.

Figure 450 – Typ 13th-year Mk 1 Mod 1 Base Fuze.