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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Why Does My British 76mm ARMDC Projectile Not Fit My Case? Scorpion Tank and Saladin
- Thread starter M8owner
- Start date
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.
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.
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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.
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.
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.
