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  1. #1
    Join Date
    24.05.2003
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    Holland
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    2,420

    Default 7,5cm SprGr. Patrone 34 fur KwK 40 and StuK 40, Germany, WW2

    Cutaway model of a 7,5cm Sprengranatpatrone 34 (High Explosive Shell 34) as used in the German 7,5cm KwK.40 tank gun of the Pzkw IV ausf. F2 (and upward models) and in the 7,5cm Sturmkanone 40 of the Sturmgeschutze III ausf.G.

    The weight of the complete cartridge is 8,71 Kg. Vo: 550 mtrs/sec.

    The projectile body is made of pressed and rolled mild steel. It is threaded in top to receive the Kl.Az 23 Nb Pr. fuze. The projectile body is filled with 0,68 kg amatol. Below the fuze a steel gaine housing is screwed containing the Gr. Zdlg. C98 Np. booster charge. A cartboard smoke generator No.8 -containing red phospor- is placed below the gaine housing. It marks the impact point of the projectile with a smoke plume. The weight of the complete projectile is 5,75 kg.

    The shellcase (patronenhulse 6339 St) is steel made (was copper clad, is gone) and is 495 mm long. It contains a bag with 0,725 Kg of Gu. Bl. P –AO powder; square flakes of powder 4x4x0,6mm. Below that, the ignition charge bag is sewed to the main charge bag, containing 20 grams of Nz Man Np powder (1,5x1,5mm). A single stick of powder is placed in the center of the bag up to the base of the projectile. The purpose of this stick is to prevent the bag with powder of falling forward during handling, losing direct contact withe the black powder magazine of the electric primer C/22 or C/22 St in the base of the shellcase. This enshures the powder charge bag is propperly ignited. A small circular pouch of K2So4 is tied to the upper part of the bag charge. It functions as a flash reducer.
    The powdercharge of this high explosive shell is much lower than the powdercharge of the Pzgr39 (armour piercing shell). This, because the high explosive shell is not depending upon impact speed. Less powder = less (recoil) wear of the gun = lower logistics and maintenance.

    Functioning of the Kl.AZ.23 Nb.(Pr). (Kleiner Aufschlagzunder 23 Nebel Pressstoff / Small Impact fuze for smoke shells 23, plastic)
    The Kl.AZ.23 Nb. (Pr) is an impact fuze made of pressed and baked bakelite powder around pressed sheet steel skelleton. This is done to save strategic material as the original Kl.AZ.23 umg was made of aluminium that became scarse. However, in functioning it was fully the same.
    The fuze exists of an outer body (1) –steel cage with bakelite., locked up by the bakelite plug (2) , which houses the firing cap housing (3). On top of the plug (2) the collar of centrifugal weights (4) is placed. The transport and firing safety on this fuze exist of a collar of six centrifugal weights, kept in inward position by a foil coil spring (5). In inward position, the centrifugal weights prevent the firing pin (6) and firing cap (red, in the firing cap housing (3) from reaching one another. A small spring (missing here) keeps them apart when the Centrifugal weights swing outward upon firing. Upon firing the centrifugal weights are thrown outward, overriding the foil coil spring (5), enabeling the firing pin and the firing cap to reach one another. Upon direct impact, the wood hammer pin (7) will push the firing pin down into the firing cap. When fired in a low angle to the grond where the projectile will graze the ground, the firing cap housing is thrown forward (negative acceleration) into the firing pin.

    The same projectile was used for the Pak 40. The Kwk.42 used the about the same projectile but with the modification of a double drivingband.

    Regards, DJH
    Last edited by PzGr40; 13.08.2011 at 22:11.
    You wanna make a piece of ammo look interesting? .......cut it!

    Looking for / Suche noch:
    -8,8cm Pzgr.40.
    -8,8cm D (drahtsperre)
    -8,8cm Pzgr.patr.Ub; Body -projectile & piercing cap- is one part, dummy base fuze.
    -8,8cm Messkartusche, (temperature gauge).
    -8,8cm Ex; Steel base and nose, rest inbetween resign.
    -8,8cm justiergranate/machine.
    -Ex ZtZ.S30 (with bearing instead of clock inside).

  2. #2
    Join Date
    24.05.2003
    Location
    Holland
    Posts
    2,420

    Default

    I removed and reposted this entire posting as I got a phonecall from member "Greif" this morning, pointing out a mistake I made with with the cutaway model of the Spgr.34 with a Kl.Az.23placed on the projectile:

    I used a Kl.Az.23 instead of a Kl.Az.23 umg (umgeandert/modified) on the SprGr 34 for the KwK.40 and StuK.40. The Kl.Az.23 umg was used on high velocity shells (KwK40, Pak40, Kwk.42), therefore it's Foil coils spring around the centrifucal weights was made of a stiffer material to prevent the fuze from arming in the barrel of the gun. The Kl.Az.23 was mainly used on low velocity artillery projectiles, so could not be used on the high velocity SpgGr. 34 of this cartridge.
    As I am not shure if there are Kl.Az.23 umg fuzes in Pr (Presstoff) type, I descided to cut up my only Kl.Az.23 Nb Pr and place it on the projectile, as this was correct according to German WW2 manuals.
    Sorry for the trouble

    Regards, DJH
    Attached Images Attached Images
    Last edited by PzGr40; 13.08.2011 at 22:06.
    You wanna make a piece of ammo look interesting? .......cut it!

    Looking for / Suche noch:
    -8,8cm Pzgr.40.
    -8,8cm D (drahtsperre)
    -8,8cm Pzgr.patr.Ub; Body -projectile & piercing cap- is one part, dummy base fuze.
    -8,8cm Messkartusche, (temperature gauge).
    -8,8cm Ex; Steel base and nose, rest inbetween resign.
    -8,8cm justiergranate/machine.
    -Ex ZtZ.S30 (with bearing instead of clock inside).

  3. #3
    Join Date
    01.10.2011
    Posts
    48

    Default Tools used in making cutaway shells...

    A most excellent example PzGr40, I am interested in your method of sectioning the parts.

    I am in the U.S., and I am a programmer of machine tools ( or was, I am in other things right now ) but for years I wrote programming for wire EDM machines ( Electronic discharge machines ) and I was wondering if you had ever used them to make the cuts for a sectioned part?

    I programmed four Agie wire EDM machines, from Switzerland, and that technology seems perfect for your application, as long as the wire will not come into contact with anything non-conductive, like pieces of wax, or bakelite or plastic , and the accuracy of the cut is in the micron range of tolerance, as well as providing an excellent finish to the surfaces exposed.

    metals like carbide, hardened steel penetrators, probably eve DU could be cut with no more effort than if it were cutting mild steel.

    Just curious if you had ever investigated this technology as a means of making these excellent models!

    I have learned a great deal in only a few weeks being here!

    V.44

  4. #4
    Join Date
    24.05.2003
    Location
    Holland
    Posts
    2,420

    Default

    Hi Vandercar,
    I especially like the last line in your posting above here. It means I am not doing all this work in vain

    What you call Wire EDM is known in The netherlands as "draadvonkverspanen". These machines are very expensive, and as money is becomming scarse on both sides of the pond I use cheaper means.
    The bigger cutaway models are cut with a handgrinder, rasped and polished, the smaller ones hacksawed, rasped and polished. It is a way of working I have practiced since 1983 and which -by now- works fastest and most easy for me.

    Above 100 mm dia. I keep a 1 mm deviation allowance in dia. and (full assembled) length on the cutaway surfaces, the flatness of the surface within 0.25/0.3mm. Below 100 mm dia I keep a .5 mm deviation allowance in dia. and (full assembele) length on the cutaway surfaces, the flatness of the surface within 0.1/0.2mm. Cut out angles are mostly appr. 90 or 120 degrees up to +2 or -2 degrees deviation over the full cutaway length, but never below 90 degrees.

    I assume you allready found the postings concerning the production methods of making a cutaway, but in case you missed out on one:

    http://www.wk2ammo.com/showthread.php?t=4225
    http://www.wk2ammo.com/showthread.php?t=4404
    http://www.wk2ammo.com/showthread.ph...hlight=hispano

    Regards, DJH
    Last edited by PzGr40; 12.11.2011 at 09:31.
    You wanna make a piece of ammo look interesting? .......cut it!

    Looking for / Suche noch:
    -8,8cm Pzgr.40.
    -8,8cm D (drahtsperre)
    -8,8cm Pzgr.patr.Ub; Body -projectile & piercing cap- is one part, dummy base fuze.
    -8,8cm Messkartusche, (temperature gauge).
    -8,8cm Ex; Steel base and nose, rest inbetween resign.
    -8,8cm justiergranate/machine.
    -Ex ZtZ.S30 (with bearing instead of clock inside).

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