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Rifles, Reloading, Optics, Equipment
Reloading
Newbie Reloader, headspace question
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<blockquote data-quote="cdherman" data-source="post: 2141482" data-attributes="member: 12282"><p>1) Yes, it can take as much as 3x firings to get new brass fully "blown out to the full dimensions of your particular chamber, especially if shooting relatively modest pressures. I was breaking in a new 7 SAUM once upon a time and I could actually measure the shoulders getting progressively longer as I went up in charge weight. I also shoot an old 6.5x55 swede that I use modest loads in. Takes 3 pops to fully expand a case. Since it has a ton of free bore, seating bullets to the rifling is impossible. I too was confused the first time it happened, having always assumed that at 50,000 PSI the brass was fully stretched.</p><p></p><p>2) This phenomena occurs more often in relatively straight walled cases. What is happening is NOT that the shoulder is not blowing out. What happens is that the firing pin pushes the loaded case forward to the shoulder, and then the internal pressure upon ignition pushes the wall out and "holds" the case in place. The head does not fully stretch back to the bolt face. This is why it is a good idea to seat bullets in new brass out to the rifling. Then the firing pin cannot push the case forward, and the excess headspace will be taken up by expanding the shoulder. </p><p></p><p>If I have a new barrel and new brass, I always break the barrel in with bullets seated into the rifling so that I can pretty much be assured that the brass is thereafter blown out to my new chambers full headspace.</p></blockquote><p></p>
[QUOTE="cdherman, post: 2141482, member: 12282"] 1) Yes, it can take as much as 3x firings to get new brass fully "blown out to the full dimensions of your particular chamber, especially if shooting relatively modest pressures. I was breaking in a new 7 SAUM once upon a time and I could actually measure the shoulders getting progressively longer as I went up in charge weight. I also shoot an old 6.5x55 swede that I use modest loads in. Takes 3 pops to fully expand a case. Since it has a ton of free bore, seating bullets to the rifling is impossible. I too was confused the first time it happened, having always assumed that at 50,000 PSI the brass was fully stretched. 2) This phenomena occurs more often in relatively straight walled cases. What is happening is NOT that the shoulder is not blowing out. What happens is that the firing pin pushes the loaded case forward to the shoulder, and then the internal pressure upon ignition pushes the wall out and "holds" the case in place. The head does not fully stretch back to the bolt face. This is why it is a good idea to seat bullets in new brass out to the rifling. Then the firing pin cannot push the case forward, and the excess headspace will be taken up by expanding the shoulder. If I have a new barrel and new brass, I always break the barrel in with bullets seated into the rifling so that I can pretty much be assured that the brass is thereafter blown out to my new chambers full headspace. [/QUOTE]
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Newbie Reloader, headspace question
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