British Bomb, 500 lb GP, Mk 4, Mk 5, Mk 6
Mk IV - The body consists of a hollow steel casting open at each end. The nose end is internally threaded to house an exploder container, which is locked in position by a locking screw. The tail end is shaped to take the tail cone, and is provided with four equally spaced slots to locate the spring clips on the tail. A male base plate threads into the after end of the body and has two threaded holes to receive the transit base bolts.
Mk V - This bomb is externally the same as the Mk IV, but has a central exploder tube instead of the exploder pockets at either end. The fuzing is in the tail only, and the nose is closed by a nose plug which has a cross cut in the end, instead of a ring as in the Bombs Mk IV.
The 500-lb. Tail No. 2 Mk I differs from the 250-lb. Tail No. 2 Mk I only in the weight and dimensions. The tail assembly consists of a tail cone with a cylindrical tail strut attached to it by four fins. It is attached to the bomb body by four spring clips.
The 500-lb. Tail Assembly No. 26 Mk 1 is similar to the 500-lb. Tail No. 2 Mk 1, differing mainly in weight and dimensions. It is used on the 500-lb. G.P. Bombs Mk IV or Mk V when carried externally on high-speed fighter aircraft, or internally on fighter bombers of the Mosquito type. The tail and fins are shorter, and it has a two-bladed arming vane instead of the four-bladed arming vane used on the Tail No. 2 Mk 1.
The bomb has a single suspension lug slightly aft of center of gravity, and secured to it by four countersunk screws.
Bomb Mk 5 was manufactured to use up existing stocks of Pistols No. 17 (long delay), which are too long to fit into the Bomb Mk 4.
Tail fins are usually painted red when a time pistol is used.
The Bomb Mk 6 is made in the US and uses fuzes manufactured there to British designs: Nose Fuze Mk 7, M3; Tail Fuze Mk 5, M1.