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What Causes a Cartridge To Do This?


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I was roost shooting with my latest batch of 20gauge reloads, 65mm Traditional Game cases refilled with 28grams of shot over a plastic obturator and 12mm fibre with crimp finish, and noticed a couple of cases thrown out by my auto had lumps torn off. Never usually happens so wondered why it should have done this time. I normally roll them but these took pretty good crimps when I made them. Any ideas?

 

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That looks like a delayed ignition to me! The primer only partialy ignites the powder compresses the wadding and then stops and then "kicks" in again causing a cavitated load situation. The progressive opening of the crimp is lost. The resulting explosion is to sudden for the crimp to open and rips the plastic from the rest of the case.

 

A mag primer may be needed.

 

A roll crimp may put more compression on the load and help it to start combustion better as may a deeper star crimp.

 

That my intial thoughts any way!

 

Underdog.

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I've rejected a few that have shown a bulge at that point, like the wad went in at angle. It almost looks like the plastic tumbled out of there!

 

I've also noticed that some manufacturers used cases (winchester for one) seem to be messy after firing round the crimp area, with slits and thinness, wondered if they are designed to not be suitable for reloading.

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Could the carts have been exceptionally cold, making them brittle ?

 

I have only seen similar damage once, from an old semi-auto that had serious pitting around the chamber, not that it will be the case here. The cases were getting blown into the pits and as the case extracted the case was getting ripped up.

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I've rejected a few that have shown a bulge at that point, like the wad went in at angle. It almost looks like the plastic tumbled out of there!

 

I've also noticed that some manufacturers used cases (winchester for one) seem to be messy after firing round the crimp area, with slits and thinness, wondered if they are designed to not be suitable for reloading.

The quality of cases for reloading is bad nowadays yes! It use to be easy to find decent cases, not any more!

 

U.

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I remember early Eley Bismuth cartridges would do this from time to time but was soon 'corrected' when they got a new batch of plastic in.

 

I guess tiny cracks could have been in the case from the fist firing that were not visible to the naked eye and they simply gave way under the 2nd firing?

 

It’s not unusual for this to happen in materials that are under high stress as far as I remember from physics module on the properties of materials. (30 years ago!)

 

David

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Guest cookoff013

has this happend to the shells you make with new cases?

 

can you tell us the recipe you use with them? plaswad or fibre?

go-on give us a clue?

 

it does look like a firing issue, not a mechanical ejection problem.

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has this happend to the shells you make with new cases?

 

can you tell us the recipe you use with them? plaswad or fibre?

go-on give us a clue?

 

it does look like a firing issue, not a mechanical ejection problem.

I've never had it happen. Just seen shells like it on the clay ground. It's Sit's post! (The info you need is in his post)

Edited by Floating Chamber
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has this happend to the shells you make with new cases?

 

can you tell us the recipe you use with them? plaswad or fibre?

go-on give us a clue?

 

it does look like a firing issue, not a mechanical ejection problem.

 

It was a fibre recipe and 3 grains of powder under the Nobelsport nominal max.

 

Over pressure should never have been an issue.

 

I don't make shells with new cases, what would be the point :hmm:

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Guest cookoff013

The point would have been, if the same happens to your new cases as the used ones, then it is the recipe.

if it happened to the once fired hulls, only then it would be the hulls.

 

what was the pressure of the previous shell?

 

The noblesports data is usually hot but, if you say you loaded fibre and 3 grains under? what was the powder? was it A)0 or slower burning?

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