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Old December 6, 2012, 11:36 AM   #29
F. Guffey
Senior Member
Join Date: July 18, 2008
Posts: 5,577
head space and the feeler gage, the companion to the press

I will assume you have a slack adjuster as in a Savage rifle with a barrel nut and you have a head space gage. The head space gage is nice but not necessary, again, I do not shoot gages, I shoot ammo. The ammo I shoot is minimum length or full length sized in my press with dies and shell holders. I have an advantage, instructions, as in barrel instillation instructions. From Douglas, two techniques and or methods, one method with a gage the other with minimum length, store bought factory ammo, then there is the other may, the transfer method/technique.

I do not insist on setting/reaming/adjusting the length of the chamber to go-gage length, without the go-gage the length of the chamber can be adjusted/reamed/set to minimum length or minimum length +. And, I make chamber length gages, they measure from –.012 shorten than minimum length to + .016” over the length of a minimum length case when measured from the head of the case to the shoulder of the case. As I have said before “I am the fan of cutting down on all that case travel”

Bad habits, the 204 is a small case, it has been assumed the case should behave in the same manner as the 270 W and 30/06 etc., when it comes to insipient (case head) separation, I have fired 8mm57 in 8mm06 chambers, there is .121” difference in length from the head of the case to the shoulder, that is interpreted as excessive head space or excessive chamber length or too much difference in length between the chamber and case when measured from the usual places. Back to Hatcher, he knew a case would not stretch .080” he knew a case that was shorter by .080” than the chamber from the head of the case to its shoulder would separate when fired, it didn’t. Hatcher became a fire former, he formed 30/06 Hatcher +.080 cases from 30/06 Springfield cases, Hatcher assumed, he did not scribe the location of the case body/shoulder juncture and shoulder/neck juncture, Hatcher assumed the case stretched. He assumed the firing pin drove the bullet, case and powder assemble to the front of the chamber shoulder, that did not happen.

Receiver designs, never discussed, it is always the “assumed” all receivers behave in the same predictable way, back to Hatcher, the design of Hatchers test rifles failed him. I have formed 30 Gibbs cases, that is .127” excessive length for the 30/06 case from the head of the case to its shoulder with no support of the case body,/shoulder, I would never attempt that with a push feed design receiver or an 03 or 03A3 receiver, but I can modify the 03-03/A3 long enough to form cases.

It is assumed the 204 separated in the usual manner, the firing pin attempts to strike the primer, the bullet, case and powder (as an assemble), in an attempt to escape the firing pin strike runs to the front of the chamber, then! the firing pin strikes the primer, pressure builds and the case locks onto the chamber and the case head moves back against the bolt face. Then separation. Consider: The case is not driven forward but held to the rear, consider the case no longer has the ability to form/fill the chamber, instead the case separates when being blown forward.

Then consider the bad habit of lubing cases ‘like bench resters’, it is necessary to remove lube from cases before firing, lubing cases is not the panacea of fire forming, lube the rear half of the case, then fire, if there is any truth to ‘case locks onto the chamber when fired, it is possible to have no lube on the front half of the case with lube on the rear half, if front half of the case locks onto the chamber with the rear half lubed it is possible the rear half could start to show signs of separation.

F. Guffey
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