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Old November 16, 2012, 11:42 AM   #3
F. Guffey
Senior Member
 
Join Date: July 18, 2008
Posts: 2,313
Bob Thompson, concerns? Your concerns warrant attention and an explanation, the failure of the primer to seat when fired means there is a difference in length between the chamber from the bolt face to the shoulder of the chamber and the length of the case from the head of the case to its shoulder. Reloaders do not have a term for this anomaly (Anomaly: something that does not ‘nomaly’ happen).

I measure the difference in length between the case and chamber, I want to know what effect the chamber will have on the case when fired, reloaders fire first to form, I form first then fire. You have low pressure loads, if the pressure was higher the primer would not protrude, it would be flush with the head of the case.

I am the fan of reducing travel time, I off set travel time with the length of the case, With reduced loads you can not form a case, the story goes something like, the bullet, case, powder and primer run to the front of the chamber to avoid the primer strike, once the shoulder hits the shoulder of the chamber the firing pin is said to crush the primer. With the shoulder of the case against the shoulder of the chamber things get serious, hot, high pressure metal cutting gas builds up and expands the case, the case when expands it locks onto the chamber wall, when this happens the case head is not supported until it hits the bolt face, and there is the problem, you case head is not being driven back to the bolt face, if it was!!!! your case would be stretching between the case head and case body, allowing the case to stretch between the case head and case body leads to incipient case head separation.

Remedy: reloaders can not get the concept of moving the shoulder forward, bump? They are all bumpers, they never talk about moving the shoulder forward without firing, and that is a bad habit, as I have just described “I am the fan of cutting down on all that case travel” and firing a case that is shorter than the chamber results in the case stretching between the case head and case body.

Case forming: I form 7MM57 cases from 30/06 cases, I form 7MM57 cases from 8MM57 cases, I form first then fire. Or I could form 30/06 cases that would chamber in my 7MM57 chambers, THEN THROW THE TEST CASES AWAY! The most important information I need to know is the length of the 7MM57 chamber from the bolt face to the shoulder of the chamber, once I know the length of the chamber I can adjust my dies to my shell holder in my press to avoid excessive sizing (reducing the length of the case from the head of the case to its shoulder), Yes I could purchase a go-gage, I could purchase a no go-gage, I could purchase a field reject gage, I choose to take advantage of the design of the press, it has threads, my dies have threads, my dies are adjustable, I am not hard headed, I use the companion tool to the press, the feeler gage (thickness gage) to adjust my die off the shell holder when adding length to the case.

Again, I have an Eddystone M1917 that has a chamber that is longer by .016” that a minimum length case, that would be the same thing? as being .011” longer than the perfect go-gage length chamber, not a problem, I form 280 Remington case to 30/06 cases, with an additional .051” case length added to the 280 Remington a good reloader can not miss, the rest? (the M1917 chamber is .002” longer than a field reject gage). It is possible to measure the length of the 30/06 chamber in the M1917 with a 280 Remington case.

I went to Alabama, knowing there was a prblem with ammo chambering I had to devise a way to check it out. I left with the instructions I was not going to fix, repair or build any computers, I was told I was not going to build and or repair engines, I was not going to build and or repair a rifle, I was told I was going for a visit. So I purchased a new box of Winchester 7mm57 ammo, every round in the box chambered, I brought back 4 boxes that would not chamber. After returning home I dug out 2 7mm57 rifles and a barrel, I attempted chambering the 4 boxes of ammo that would not chamber in the rifle in Alabama, 1 round of the 40 offered resistance to bolt closing, the rest chambered. The rifle in Alabama has a chamber that is shorter by .002” than a go-gage length chamber, I will measure the length of the cases that would not chamber in the Alabama rifle, no, I do not use a head space gage, I do not use a case comparator, back to the extra barrel, no matter the hype about the tools, it is about understanding the tool, I can use a barrel to measure the case head protrusion to determine the length of the case.

I returned home with a computer, I had to sneak up on that one to get it started.

F. Guffey
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