Casehead Separation (photo and question)

Wooly ESS

Wooly ESS

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270_casehead_separation.jpg


The cartridge case above is a 270Win. It was fired from a Winchester M70. I purchased the rifle new in 1990 and have shot several hundred rounds through it. The brass is about the same vintage as the rifle, and has been reloaded several times. Some of the loads were fairly hot, but none exceeded the recommended max for that powder and bullet. This particular reload held 58.5gr H4831 behind a 130gr Hornady SST. I have gone up to 59.5 gr with sticky extraction and backed off a grain. In the same group of six rounds, one other case separated like this one.

I don't think the problem lies with the rifle, as this has never happened before in the 16 years I have had the gun. I tend to suspect faulty reloading techniques combined with worn brass.

Does anyone have any ideas as to why this may have happened?
 
the problem is worn out brass, after just so many reloads the brass gets hard and will crack and split. put this lot of brass in the scrap bucket and get some new once fired brass and you should have no more problems.
 
Cases that are being used at maximum loads + well-used brass that has been full-length re-sized too often often separate like that. Sometimes a rough chamber makes the problem worse, especially with work-hardened brass.

Not setting your full-length sizing dies properly and setting the shoulder back excessively on each resizing also excaberates the problem.

A bolt face that is badly out-of-square with the centre-line of the chamber will also cause case head separation like yours but it usually shows after only 2 or 3 reloadings of a new case.
 
it wouldn't hurt to get a "no go" guage to make sure your chamber isn't stretched. over time using hot or even warm loads has been known to stretch a chamber.

i'm not ruling out worn out brass.
 
Check your other brass from that same lot and see if any have a bright line starting to show in the same area as this crack; you might also be able to feel a crack starting from the inside, using a hooked dental pick or piece of wire bent to shape.
 
Or section a casehead and see if a groove is forming internally.
It can be a good idea to size your brass for your rifle; don't just run the case into the die until the shellholder makes contact.
 
The number one reason for case head separation is oversizing the brass, proper die adjustments and the use of a neck sizer goes a long way in preventing this occurence.
bigbull
 
I have gone up to 59.5 gr with sticky extraction and backed off a grain.
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Of the six rounds in this lot, two suffered separation and the remaining four have bright lines circling the case.
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Based on these two observations, I would speculate that the action has developed some excessive head space due to an unfortunate combination of components, chambering tolerences, etc. Bright lines encircling the case near the head ARE DEFINITE SIGNS OF IMPENDING CASE SEPERATION, so ALL of your cases WILL seperate. Sticky extraction is indicative of peak pressures BEYOND PROOF LOADS........SOME COMBINATION IS RESULTING IN PRESSURES BEYOND DESIGN TOLERENCES FOR THE ACTION..........HAVE IT PROFESSIONALLY INVESTIGATED!
 
rmkm70 said:
it wouldn't hurt to get a "no go" guage to make sure your chamber isn't stretched. over time using hot or even warm loads has been known to stretch a chamber.
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:confused: :confused: :confused: Stretched chamber? Bulged maybe, but stretched?? Eagleye
 
Thank you all for your feedback. The general consensus is that I have been shoving the case shoulder too far back on resizing. My first step will be to throw out ALL my used 270 brass. It doesn't owe me anything by now anyway. My next step will be to buy some new brass and back my sizing die out a bit. If my new brass survives firing unscathed, I will consider my problem solved.
 
I believe you can have the head space checked however,you stated that the brass is about the same age as your rifle and no brass no matter how carefully you size and load will last forever.Cases can last from 5 to 20 reloads depending on calibre and pressures.
Scrap your brass start with new working your loads up from the start again.This is my opinion.
 
I would also suggest that you back your load off a bit more, too. One grain back from an overpressure load is still a hot load. In my opinion the energy drop that would result from backing off another grain is negligible but your case life will be greater and often your accuracy may even be a bit better. Although you likely will want full length sized rounds for hunting, neck sizing only for your practise ammunition will extend your case life by a lot.
 
Why not? said:
High pressure does not stretch brass longitudinally to cause head separations like that pictured. Excessive headspace does. :(

Ted
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Chambers are cut to be within given tolerances; too large the case fails, too small the cartridge does not chamber. This is not to say that excessive headspace does not occur, but I do not believe that is the situation here.

Because the cartridge needs to chamber in the rifle, the cartridge's dimensions cannot be exactly the same as the chamber's dimensions. Most bottle neck cartridges lengthen with each firing, which is why we trim our brass every so often. The brass flows forward from just in front of the case head, and over subsequent firings the case becomes too thin in this area, and it fails as shown.
 
I think you should go buy and READ a couple of reloading manuals, since every manual in publication shows and explains how this happens.
 
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