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  1. #1
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    Why Does My British 76mm ARMDC Projectile Not Fit My Case? Scorpion Tank and Saladin

    I finally got all the parts together for a HESH round, and the case mouth is much bigger than the projectile. I have seen cases expand on firing, but not this much. Is this normal? This is a fixed round, correct? Thank you for your help.
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  2. #2
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    Fire formed in a really oversized or worn chamber?

    Make up a die to re-size it, you have mad skills!

  3. #3
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    The fired ones always seem oversize. I don't know why.
    ___HAZ/
    _____/ORD Hazardous Ordnance Recognition
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  4. #4
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    I just found a 2016 dated post on this site from one of our UK members that says you cannot seat a projectile in a fired case due to how much it expands at the neck. It is time to make a new die.

  5. #5
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    There has to be some oversize in the breech to enable the round to chamber easily
    When the propellant gas pressure forces the projectile out of the case, the pressure is in the order of 20 tons psi, which forces the case to expand into any breech void. In the case of cased APFSDS this may be as high as 35 tons psi. On cooling it may contract slightly to prevent hard extraction, but it does not go back to its original diameter. It takes about 6 tons psi to get projectiles with driving bands to engrave into the rifling.
    The expansion is magnified when the gun goes from new gun to 1st quarter, 2nd quarter, 3rd quarter and 4th quarter.
    Last edited by AE501; 8th May 2018 at 04:01 PM.

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    HAZORD (8th May 2018)

  7. #6
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    I have used a cast iron cone shaped thing to resize one of these once and it was difficult due to the thickness of the metal
    in these particular cases, but it can be done. I do agree the expansion in these seem much more than one usually encounters
    in other fired cases.

  8. #7
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    Unfired ones can sometimes be found. I bought one at a flea market back around 2010 but have since sold it on to another collector.

  9. #8
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    try and find a Blank case as these do not expand as there is no build up of pressure in the chamber before the shell starts to move and they will hold a proj. reasonably tightly. They are often easily identified as they still have 'BLANK' stencilled on the base.

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    reccetrooper (12th May 2018)

  11. #9
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    I try to find the best fitting case,and sit the projectile on a shaped block of wood for the correct height.
    The ARMDC 76mm cases are notorious for over sizing.

  12. #10
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    Right. The die has been cast (or machined in this case). The case resized with great ease. Problem sorted.
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    enrico959 (19th May 2018)

 

 

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