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I want to form fire new brass to the chamber of my .308 rifle before neck sizing and loading hunting rounds.
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Hook69, I chamber a round, pull the trigger and then eject a once fired case, I do not need to add the title of ‘fire former’ to my resume. Before I pull the trigger on a minimum length/full length sized case I measure the length of the case from the shoulder to the head of the case. No one does that, but me. I verify the case is minimum length/full length sized, after firing the case I measure the length of the once fired case from the shoulder to the case head, this means nothing to anyone, but me. I want to know the difference in length between the chamber from the shoulder to the bolt face and the length of the case from the shoulder to the case head. I want to know the effect the chamber has on a new, factor minimum length sized case when fired.
The reason know to no one is why. Why would I want to know the difference in the two lengths? I ask questions like: “How do you do that?” “How would you check that?” Before I can get an answer members of forums turn into Incognito personalities.
I want to know: STRETCH, it is assumed cases stretch, as Bart B. starts with ‘The firing pin strikes the primer, then the complete package including the case, powder and bullet takes off in an attempt to out run the firing pin etc.. Step sequence, I insist he is leaving out a couple of steps, I insist he is omitting a factor or two. I have scribed cases before firing at the shoulder/case body juncture, strange to everyone but me, the scribed line at the shoulder/case body juncture did not move, and I ask “What does that prove?”
Add to resume? I am a case former, I form cases before firing, I form 308 W cases from 30/06 cases.
http://www.saami.org/PubResources/CC...Winchester.pdf
http://www.saami.org/PubResources/CC...pringfield.pdf
The difference in length from the shoulder of the case to the case head for the .308W is 1.559, the 30/06 length from the shoulder case body juncture to the case head is 1.948. To form a 30/06 down to 308W the new shoulder is formed .389” further back. The difficult part to understand the new shoulder is not the original shoulder that has been moved back, the formed shoulder for the 308W is a new shoulder and the old shoulder has been erased and becomes part of the shoulder and neck.
Fire forming, it is assumed all the stretch is between the case head and case body, when I form first and fire there is no stretch between the case head and case body.
Then there are the folks, I do not know who you are so I suggest you ask Bart B.. like “Bart B., am I a ‘folks?’. Some could assume I form all of my cases, the answer is no, if I want to measure a chamber for length I form a case, it is not necessary to start over everyday. I can form a case to determine the length of the chamber then use that case to transfer that dimension to a comparator, sizing die, I do not mind going to the range to fire cases, I do not find it necessary to go to the range to fire form because I form first then fore.
Then there is fire forming, not the topic of the OP question. I have wildcat type chambers, it is necessary to form those cases and then fire to finish. Fire forming finishes the forming process, after firing the case to form the shoulder and case body the case becomes a once fired case.
F. Guffey