pzgr40
Well-Known Member
Cutaway model of two WW2 British 3” (76,2mm) mortar shells; a HE shell and a WP smoke shell, as used in the Ordnance M.L. 3” mortar. Originally , the 3” mortar was taken into service in march 1917 and slowly but surely developed into the Mk.2 version in 1939. However this version still lacked range. The propellant used was changed and the range increased from 1600 yards max. to 2750 yards. The 3” mortar Mark 4 had a heavier baseplate and an improved sight, the Mark5 was a lighter version of the weapon, meant for the far east. Only 5000 were built.
The 3”mortar was used by all Commonwealth countries.
The shells had a range of 2750 yards (2516 mtrs) maximum, and 125 yards (114 mtrs minimum).
The bomb had a Vo. of 223 mtrs/sec (731 ft/sec) and a weight of 4,54 kg (10 Lb).
The length of the complete round is 398mm, with the safety cap removed the length is 394mm (pict. 04).
The filling of the HE bomb was a 450 grams mixture of Ammonium nitrate and TNT (Amatol) 80/20 or 60/40 or 55/45.
A cartboard packed Tetryl booster is placed just below the fuze.
A ring shaped layer of pure TNT topping is cast on top of the explosive charge.
The WP smoke bomb was filled with 680 grams White Phosphor. A steel bushing is placed in the shell body to keep the WP charge separated from air and oxygen. A small Tetryl bursting charge is placed below the fuze to split the bomb body and spread the burning White phosphor. Except for producing smoke screens, the WP bomb is also suitable as an incendiary bomb, either against personnel.
The propelling catridge has a charge of 4,5 grams Ballistite B16. An interesting item on the propelling cartridge is the ring pressed over the rim of the shellcase. It contains a brass plate to which a firing pin is connected. This means every bomb has it’s own firing pin, the weapon has does not need one.
Incremental charges can be added to the tailfins to in- or decrease range; 6 incremental charges of 12 grams, either 3 of 18 grams, either 4 of 12 grams , either 2 of 18 grams ranging from long range to short range.
The fuze used on this bomb is the fuze DA 152 (Direct Action). The body of the fuze is made of cast zinc. It contains the spring loaded firing pin, the sping loaded rotation shutter (housing the firing cap), The brass detent and the detent spring and the detent ball. The lower part houses the magazine, containing a C.E. pellet. On top of the fuze hoausing a thin brass cap is crimped in place. This brass cap is protected by a Zinc protection cap which is screwed to the top of the fuze.
Functioning of the Fuze:
Before firing, the zinc transport cap is screwed off – as the text on top says: remove before firing- , exposing the brass safety cap.
Upon firing, inertia sets back the brass detent pin –riding it’s spring-, enabling the detent ball to roll down the channel. After the acceleration has stopped the detent pin moves upward again untill it is blocked by the ball (see fuze picture: after firing). The firing pin is forced up by the firing pin spring, thereby releasing the spring loaded rotation shutter that is held in off line position by the point of the firing pin in the safe position. The shutter now rotates under the firing pin. On impact the brass cap is crushed inward , forcing the firing pin into the firing cap, which ignites the C.E. pellet magazine. This will ignite the booster and the main charge.
Regards DJH
The 3”mortar was used by all Commonwealth countries.
The shells had a range of 2750 yards (2516 mtrs) maximum, and 125 yards (114 mtrs minimum).
The bomb had a Vo. of 223 mtrs/sec (731 ft/sec) and a weight of 4,54 kg (10 Lb).
The length of the complete round is 398mm, with the safety cap removed the length is 394mm (pict. 04).
The filling of the HE bomb was a 450 grams mixture of Ammonium nitrate and TNT (Amatol) 80/20 or 60/40 or 55/45.
A cartboard packed Tetryl booster is placed just below the fuze.
A ring shaped layer of pure TNT topping is cast on top of the explosive charge.
The WP smoke bomb was filled with 680 grams White Phosphor. A steel bushing is placed in the shell body to keep the WP charge separated from air and oxygen. A small Tetryl bursting charge is placed below the fuze to split the bomb body and spread the burning White phosphor. Except for producing smoke screens, the WP bomb is also suitable as an incendiary bomb, either against personnel.
The propelling catridge has a charge of 4,5 grams Ballistite B16. An interesting item on the propelling cartridge is the ring pressed over the rim of the shellcase. It contains a brass plate to which a firing pin is connected. This means every bomb has it’s own firing pin, the weapon has does not need one.
Incremental charges can be added to the tailfins to in- or decrease range; 6 incremental charges of 12 grams, either 3 of 18 grams, either 4 of 12 grams , either 2 of 18 grams ranging from long range to short range.
The fuze used on this bomb is the fuze DA 152 (Direct Action). The body of the fuze is made of cast zinc. It contains the spring loaded firing pin, the sping loaded rotation shutter (housing the firing cap), The brass detent and the detent spring and the detent ball. The lower part houses the magazine, containing a C.E. pellet. On top of the fuze hoausing a thin brass cap is crimped in place. This brass cap is protected by a Zinc protection cap which is screwed to the top of the fuze.
Functioning of the Fuze:
Before firing, the zinc transport cap is screwed off – as the text on top says: remove before firing- , exposing the brass safety cap.
Upon firing, inertia sets back the brass detent pin –riding it’s spring-, enabling the detent ball to roll down the channel. After the acceleration has stopped the detent pin moves upward again untill it is blocked by the ball (see fuze picture: after firing). The firing pin is forced up by the firing pin spring, thereby releasing the spring loaded rotation shutter that is held in off line position by the point of the firing pin in the safe position. The shutter now rotates under the firing pin. On impact the brass cap is crushed inward , forcing the firing pin into the firing cap, which ignites the C.E. pellet magazine. This will ignite the booster and the main charge.
Regards DJH
Attachments
Last edited: