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Case Head Separation: Causes and Cures
I know cases can be expensive, but none cost as much a trip to a gunsmith or a ruined hunting trip. Discard suspicious brass. You will be money ahead in the long run.
Last week, a friend of ours brought in a rifle that had suffered a head separation. When manuals caution handloaders to monitor cartridges for incipient head separation, this is the event they are trying to prevent. Suffering a head separation can do more than end a hunting trip, which it does very well; it can also damage the rifle by allowing high-pressure gas to cut the chamber making extraction more difficult. The cause is almost always old, well-used brass.
In the case of our friend, this was his second trip into our shop for his .270 Winchester this year. The first had involved a cartridge head stamped .30-03 which was the original chambering for the 1903 Springfield and discontinued in 1906. No one could have seen trouble on the horizon with that one. The more current problem occurred with a comparatively newer Winchester Super Speed case that was still old enough to have voted for Nixon.
In both instances, the cartridges had exhibited the bright line ahead of the cartridge web that signals incipient separation. Case head separation is caused by the firing and resizing process which requires the case to stretch and then be re-compressed. Full-length sizing works the brass more that neck sizing by pushing the shoulder back to allow for easy chambering at the cost of more case stretch as it re-fills the chamber back to its headspace dimension.
The point of stretch is located above the solid web of the case, which when cut open, reveals a well-defined thinner ring. This ring will eventually become the fracture point of a case head separation. When the head separates, it can be very hard to remove, especially in the field.
My favorite way to remove the case body from a chamber is to use Cerrosafe. If you don’t have this in your stock of gun supplies, it is well worth purchasing. It is sold in ingots that look like a cross between lead and solder. With a melting point of between 158° to 190° F., Cerrosafe melts in boiling water in the same manner as paraffin or chocolate. During the first 30 minutes if cooling, it shrinks and then returns to 100% of its cast size within an hour. Gunsmiths and shooters use it to determine chamber dimensions and access the quality of a reamer’s cut. It also does a great job removing a headless case.
To remove the case, push a patch into the bore ahead of the case mouth. It is only necessary to seal the bore, not block it to the point that it is difficult to move the patch. The rifle steel will cool the Cerrosafe very quickly preventing it from running.
Melting with water is probably safer, but is a real inconvenience in a machine shop. Like most, we used a torch to heat the Cerrosafe until it ran freely. Once melted, it was carefully poured into the chamber with the muzzle pointing downward. After a few minutes a rod was used from the muzzle end to gently tap out the case and the chamber casting.
Once cleared and cleaned, another casting should be made of the chamber to check for any damage caused by gas cutting from the failed case. If you have a bore scope, it should also be used to make sure no permanent damage has been done to the chamber.
Case head separations are just part of handloading, but they can be avoided by thorough case examination after each firing. The visible bright line that shows a case head is about to fail is more easily seen on cleaned brass, so make sure to inspect the brass once it has emerged from the tumbler. I know cases can be expensive, but none cost as much a trip to a gunsmith or a ruined hunting trip. Discard suspicious brass. You will be money ahead in the long run.