Measuring pressure by measuring case web/head

jasonk

Very Snipery
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Feb 23, 2007
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First of all, I can't find a real answer on whether case web and case head are the same thing, so I apologize if I use the term incorrectly.

I've heard flattened primers isn't a great indicator of pressure. I hear that case web expansion is the better way to look for over pressure.

I was given some 338 Norma Magnum brass recently, a few new pieces and some once fired with no load data on what was fired through them. Measuring with calipers, what I think is the case web (right in front of the extractor groove), the unfired new brass is all at .582 and the once fired is .586 to .589. It's rumored that they were shot at 70k psi....

Assuming that I can size them and they'll fit in my rifle....Is the once fired brass good to reload or have they been subjected to to much stress?
 

former naval person

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Re: Measuring pressure by measuring case web/head

Maybe. But, 1, they may not size down enough to fit your chamber. A matter of how far down the case your die set sizes. And, 2..the primer pockets may, and probably are, loose. So...limited case life in your gun, plus chance of leaky primers scarring/ruining your bolt face, and, since you need to work up loads with that particular case...you have used up the remaining reloading life before you have gotten real use out of them. Rule of thumb (in my estimation) is, that if the case head is more than .0015 over the unfired case, and on subsequent firings if it keeps expanding, you have exceeded the pressure standard. 70K is 5K over MAXIMUM psi. That said, Norma exceeds that expansion on factory loads for the Weatherby cartridges. What do I know? Be careful. JMHO
 

1SMALLJOHNSON

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Re: Measuring pressure by measuring case web/head

Depends on who you're asking. Some bozo on this forum tried to reload some .50 BMG proof cases (been fired). I tried nicely to explain to the gentleman that it was not a good idea. (Maybe that was biggerhammer....)

As to your question on web expansion: You don't know if the larger sized stuff came from the same brass lot. Do you? If so, and if they were, it's likely that these cases saw some pressure. I'll measure my before and after Norma to determine what I was seeing for expansion. Yes, .338 Norma. If you don't hear from me in a day, PM me and tell me to get my ass in gear.

I'd venture a guess that those rounds saw more than 70kpsi. That's a tad bit bigger than I'd expect. I measure just forward of the extractor cut.
 

jasonk

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Feb 23, 2007
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Re: Measuring pressure by measuring case web/head

Thanks guys...I look forward to hearing from you 1smalljohnson.

The brass was free, so I'm not complaining, just wondering if it's worth trying to save. I may try to deprime and see how loose the pockets are with new primers....just hate to waste good primers these days
smile.gif
 

1SMALLJOHNSON

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Re: Measuring pressure by measuring case web/head

My virgin cases measured between 0.582 and 0.583, just forward of the extractor cut. Fired case, which I know to have been shot at 63,500 psi, measured 0.585.

Keep in mind that the rough figure for web expansion should best be described as % of change, rather than only a raw number. 0.002" increase on .223 ammunition does not relate to same increase in a much larger case, as with .338 Norma.