Cutaway model of a British QF 25 pounder BE smoke shell from the WW2 Q.F. 25 Pdr. Mark 1 & 2 gun. This excellent gun was originally of British WW2 design, it was however used by many other allied countries, as well as by the Germans, whom designated the captured guns the: 8,76 FK 280(e). The Netherlands army kept these guns in stock (reserve) until about 1980, Pakistan still keeps the gun in reserve and still manufactures ammunition for the gun (POF).
Muzzle velocity of shell :532 m/s (1745 ft/sec)
Range 12.253mtr.( 13.400 yards).
The shell is fuzed with the pyrotechnic time and percussion (graze) fuze No.:221.
The shell consists of a steel body in which three smoke canisters are placed. Above these canisters a steel ejection flange is placed with a small hole in the center. Above the expulsion flange a bag with coarse black powder is placed, acting as the expulsion and ignition charge for the smoke canisters.
The smoke canisters have a through hole in which a thin pipe with sideway holes is placed. Around this pipe the ignition charge (black) for the smoke compostion (gray) consisting of Hexachloroethane is pressed. The smoke composition is ignited at the same moment the smoke cannisters are ejected from the base of the projectile.
The base of the shell is closed with a steel flange which is held in place with a brass ring with two twists of thread. For this ‘weak’ configuration is chosen as the force of pushing out the base plate cannot be too large as this would result in the canisters being crushed and getting stuck in the shell body.
The space between the base flange and the rim on the inside of the shell body is filled with a copper plate which acts as a gasket, preventing burning gasses from entering the shell body upon firing. The space above it is filled with steel and cartboard washers as to prvent axial movement of the smoke canisters. A cartboard ring is placed between the smoke canisters.
Time and percussion (graze) fuze No.:221 (pict.02)
The igniferous time and percussion (graze) fuze No.221 consists of a brass body (1) with a recess in the bottom in which the gunpowder magazine (2) is housed, closed with a brass cap (3). The top of the igniter body is tubular and has three longitudal holes drilled side by side. In the center hole, the graze fuze is placed, consisting of a firing pin (4), a spring above it and a firing cap (5) at the nose end. In rest, the firing pin is kept fixated by a radial safety pin, which -on it’s turn- is fixated by a setback pin (the radial safety pin and set back pin are not visable in this cutaway model, they fall away behind the pyrotechnic channels). The third channel houses a setback firing cap (6) on top of a spring (7). A firing pin (8) is placed below the spring. Two brass rings (9 and 10) with a igniferous composition are arranged around this tubular part, which form the time setting part of the fuze. The lower ring (10) is rotatable to set the time -maximum 50 seconds-, the upper ring (9) is not rotatable and is fixed by means of an axial pin. Both rings are locked up by an bakelite nose cap (11).
The fuze functions as follows; before firing, the time is set by rotating the lower ring (10) counterclockwise. The further it is rotated, the longer the burning time of the igniferous composition and –consequently- the delay. When fired, the percussion cap (6) moves backward due to inertia and hits the firing pin (8) riding the spring (7). The flame from the exploding percussion cap ignites the igniferous composition in the upper ring (9). A hole is drilled upwards in the lower ring so that the flame flashes from the upper to the lower ring when the burning igniferous composition has reached this hole. The fuse composition will burn until it reaches the hole to the magazine (12) in the flange of the fuze and the magazine (2) is ignited. The flame emerging from the bottom of the fuze ignites the bag with black powder which ignites the smoke canisters and ejects them from the shell body.
The reason for using two igniferous composition rings is twofold; the first reason is that one does not have to press the composition too hard so that the composition is not 'pressed to stone' and can therefore refuse to burn. The second reason is to divide the error that occurs with the direction of rotation of the shell and the burning direction of the fuze, during one half of the burning time the flame is pushed into the composition ring by the direction of rotation of the shell, the other half - if the flame has moved to the lower ring - the flame runs behind the composition while it burns. Since the length of the fuse to be burned in the upper and lower rings is the same, so the error in burning time is mediated.
The three base ejected smoke canisters land on a distance from one another forming a wide smoke screen, hence the name ‘screening smoke’.
Regards, DJH
Muzzle velocity of shell :532 m/s (1745 ft/sec)
Range 12.253mtr.( 13.400 yards).
The shell is fuzed with the pyrotechnic time and percussion (graze) fuze No.:221.
The shell consists of a steel body in which three smoke canisters are placed. Above these canisters a steel ejection flange is placed with a small hole in the center. Above the expulsion flange a bag with coarse black powder is placed, acting as the expulsion and ignition charge for the smoke canisters.
The smoke canisters have a through hole in which a thin pipe with sideway holes is placed. Around this pipe the ignition charge (black) for the smoke compostion (gray) consisting of Hexachloroethane is pressed. The smoke composition is ignited at the same moment the smoke cannisters are ejected from the base of the projectile.
The base of the shell is closed with a steel flange which is held in place with a brass ring with two twists of thread. For this ‘weak’ configuration is chosen as the force of pushing out the base plate cannot be too large as this would result in the canisters being crushed and getting stuck in the shell body.
The space between the base flange and the rim on the inside of the shell body is filled with a copper plate which acts as a gasket, preventing burning gasses from entering the shell body upon firing. The space above it is filled with steel and cartboard washers as to prvent axial movement of the smoke canisters. A cartboard ring is placed between the smoke canisters.
Time and percussion (graze) fuze No.:221 (pict.02)
The igniferous time and percussion (graze) fuze No.221 consists of a brass body (1) with a recess in the bottom in which the gunpowder magazine (2) is housed, closed with a brass cap (3). The top of the igniter body is tubular and has three longitudal holes drilled side by side. In the center hole, the graze fuze is placed, consisting of a firing pin (4), a spring above it and a firing cap (5) at the nose end. In rest, the firing pin is kept fixated by a radial safety pin, which -on it’s turn- is fixated by a setback pin (the radial safety pin and set back pin are not visable in this cutaway model, they fall away behind the pyrotechnic channels). The third channel houses a setback firing cap (6) on top of a spring (7). A firing pin (8) is placed below the spring. Two brass rings (9 and 10) with a igniferous composition are arranged around this tubular part, which form the time setting part of the fuze. The lower ring (10) is rotatable to set the time -maximum 50 seconds-, the upper ring (9) is not rotatable and is fixed by means of an axial pin. Both rings are locked up by an bakelite nose cap (11).
The fuze functions as follows; before firing, the time is set by rotating the lower ring (10) counterclockwise. The further it is rotated, the longer the burning time of the igniferous composition and –consequently- the delay. When fired, the percussion cap (6) moves backward due to inertia and hits the firing pin (8) riding the spring (7). The flame from the exploding percussion cap ignites the igniferous composition in the upper ring (9). A hole is drilled upwards in the lower ring so that the flame flashes from the upper to the lower ring when the burning igniferous composition has reached this hole. The fuse composition will burn until it reaches the hole to the magazine (12) in the flange of the fuze and the magazine (2) is ignited. The flame emerging from the bottom of the fuze ignites the bag with black powder which ignites the smoke canisters and ejects them from the shell body.
The reason for using two igniferous composition rings is twofold; the first reason is that one does not have to press the composition too hard so that the composition is not 'pressed to stone' and can therefore refuse to burn. The second reason is to divide the error that occurs with the direction of rotation of the shell and the burning direction of the fuze, during one half of the burning time the flame is pushed into the composition ring by the direction of rotation of the shell, the other half - if the flame has moved to the lower ring - the flame runs behind the composition while it burns. Since the length of the fuse to be burned in the upper and lower rings is the same, so the error in burning time is mediated.
The three base ejected smoke canisters land on a distance from one another forming a wide smoke screen, hence the name ‘screening smoke’.
Regards, DJH
