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40x157R pom pom high explosive shell

pzgr40

Well-Known Member
Premium Member
Cutaway model of a WW2 British 40x157R pom pom high explosive shell as used in the QF 2 pounder AAA. (Anti Aircraft Artillery)

Functioning of impact fuze D.A No.243. (D.A = Direct Action);
The fuze consists of a fuze housing (1), the booster housing (2), and the housing (3) for the set back safety mechanism (4,5,6) and the firing cap (8).
Upon firing, the conical part of the safety ferulle (4) bends open and moves downward together with the arming ring (5). This releases the two collar halves (6), enabeling them to move outward due to the centrifugal force. The firing pin (7) can now reach the firing cap (8) upon impact. After firing, the shutter (9) rotates around it’s pivot pin, replacing the blind hole in the centerline of the fuze for a detonator. The fuze is now fully armed. Below the shutter (9), a stemming charge (10) is placed in a steel insert, ending in the booster charge (11).
Upon inpact, the firing pin (7) is pushed in the firing cap (8) which explodes. The flame travels down the channel into the detonator of the shutter (9), which explodes. The flame travels down the stemming section (10) into the booster charge (11), exploding the main chartge of the shell.

In the base of the projectile the “tracer and igniter shell No.7 Mk.IV” is screwed. This mechanism has a set back firing cap installed, fixated by a stirrup spring. This assembly is placed into a cup with an internal firing pin, locked up by a lead (melting) ring in the base of the projectile. Upon firing, the firing cap moves downward into the firing pin, igniting the tracer composition. After leaving the barrel, the pressure in the igniter rises due to the burning tracer composition until the cup together with the set back firing cap are thrown out and the burning tracer is now visable. After burning up, the tracer composition ignites the gunpowder in the brass cup in top of the tracer igniter mechanism. This initiates the self destruction of the shell.

Above the tracer igniter a black powder pellet is placed with a cartboard disc above it. A TNT pellet is placed below the booster. Around this central exploder assembly ,a cartboard tube is placed. The main filling of the shell is cast TNT.

The brass shellcase is 157mm long and is filled with a bundle of appr. 100mm long sticks of cordite, tied together with two strands of silk thread.
A piece of tin foil is placed on top of the powdercharge, the tin foil acting as a decoppering agent; the tin evaporates upon firing the round and forms a hard and brittle alloy with the copper of the driving band remaining in the corners of the lands and grooves. The driving belt of the next round pushes this alloy out of the barrel, thus keeping the barrel free from fouling.

Regards, DJH
 

Attachments

  • Pict. 01 - 40x157R 2 pounder pom pom.JPG
    Pict. 01 - 40x157R 2 pounder pom pom.JPG
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  • Pict. 02 - 40x157R 2 pounder pom pom cutaway.jpg
    Pict. 02 - 40x157R 2 pounder pom pom cutaway.jpg
    214.7 KB · Views: 119
  • Pict. 03 - 40x157R 2 pounder pom pom fuze 243.jpg
    Pict. 03 - 40x157R 2 pounder pom pom fuze 243.jpg
    270.7 KB · Views: 91
  • Pict. 04 - Tracer-igniter SD  No.7 Mk.IV.jpg
    Pict. 04 - Tracer-igniter SD No.7 Mk.IV.jpg
    59 KB · Views: 73
  • PIct.05 - MkVIIIpompomsHMSRodney1940.jpg
    PIct.05 - MkVIIIpompomsHMSRodney1940.jpg
    52.3 KB · Views: 74
Thank you:tinysmile_shy_t:. More 2 pounders cutaways to follow in the near future.
 
No string of words in the, English language to properly describe your talent and skills in the field. Just spectacular in every way.

Jason
 
Thank you all for the very nice comments. I'll make shure I keep posting :tinysmile_shy_t:
 
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