fire forming and mistakes
Quote:
Originally Posted by
Jonnytoobad
Hey everyone
A few months ago I bought a sporterized Peruvian Mauser Modelo 1932 (VZ 32 BRNO made action ) and it had been re-done many years ago. The original stock removed and a walnut Fajen commercial stock was added, it's ancient hard rubber but pad had gotten solvent on it at some point and is partially melted. The original military barrel was countoured/turned-down to a light profile and a set of Williams sporting irons sights were added to the barrel. The bolt handle was extended and bent down and welded with nickle rod,its tall stripper clip guide was ground off and the receiver was drilled and tapped for an unknown and now missing set of rings. Add to that a light layer of rust and 7.65Argentine chambering and you have a $100 dollar donor rifle.
I also found a 1896 Swedish Mauser barrel that had a broken receiver still attached dated 1899 and made at Carl Gustave. Though the Receiver was totaled but the barrel was in EXCELLENT condition!!!! So for a $100 dollar bill I got both the rifle and the barrel!!! And since I new the 1932 Peruvian is a 98 but a small I ring I knew was good to go with the older Swedish Mauser barrel...
Despite deciding to re-barrel the rifle I have been holding out for a box of 7.65x53mm ammo to turn up just so I could shoot the rifle before re barreling it. And eventually this week I came across a partial box of 150 grain Norma factory 7.65ARG.
Just perfect....Or so I thought....
So I headed to the range with my 6 rounds and a shoot and see target and my spotting scope. I found a spot at the 50 yard line set up my target. Got into sitting position and fired a single shot.
The rifle made a strange sound almost like a clang and had very little recoil. I ejected the spent casing and it looked very strange...the case had a shoulder but no neck... there was a deep ring (almost a a crack) half way around the web of the cartridge case (thank goodness for Norma Brass) also the primer was flattened and had spread deeply into the pocket. The 7.65 Argentine had fire formed into another cartridge.
I did not fire another round...I headed home to do some comparative inspection. I compared it to the .308 and it was far too long....so I compared it to a .30-06...Bingo...the chamber had be re bored. Next I attempted to chamber a .30-06 case and it was super tight, I had a hard time opening the bolt when I did a un-bulleted cartridge came out! I took a metal cleaning rod and punched out the stuck bullet. So not only was it re chambered to .30-06 this had been done rather poorly and was too short.
Looks like my idea to re-barrel it to 6.5x55SE was a correct choice....as soon as I get an action wrench that .31-06 wildcat barrel is coming off and getting cut up.
So a word to the wise always pour a chamber cast.
Jonnytoobad
http://milpas.cc/rifles/ZFiles/Bolt%...0Info/peru.htm
When recommending a chamber case it is always assumed the person doing the chamber cast reads the instructions, there is no shortange of cerosafe around here, I do not use it.
I measure the length of the chamber first, firing a 308 W in a 30/06 chamber will not cause high pressure, in fire forming time is a factor, before the pressure can get serious the case must fill the chamber, and that take time.
Firing a 7.65mm53 in a modified 7.65mm06 chamber does not cause high pressure, after firing the 7.65mm53 in the 7.65mm53 chamber the case is ejected as a 7.65mm06 case with no neck and a hint of a shoulder, the case shortens when the case fills the chamber, the neck is pulled back and becomes part of the case body and that little hint of a shoulder.
I have fired 8mm57 cases in an 8mm06 chamber, cases after firing came out looking like 8mm06 cases with out necks and a hint of a choulder.
Head space: The difference in length between the 7.65mm57 and the 7.65mm06 is .188 meaning the shoulder of the 7.65 is off the shoulder of the 7.65mm06 .188, the case is held to the rear of the chamber with the extractor causing the case to fill the chamber, PROOF: No neck, had the case case head space on the shoulder the case would have had to stretch .188 between the part of the case that locks to the chamber and bolt face. EXCEPTION: Bench resters that grease their cases for slide and glide shooting.
When shooting 8mm57 ammo in a 8mm06 there is .121 difference in length between the head of the case and shoulder of the case, when the 8mm57 is fired in the 8mm06 chamber the case body part if the shoulder and the neck of the case becomes part of shoulder, again, meaning the extractor held the case to the rear and the case filled the chamber. Then there is that other mistake, shooting 8mm ammo in a .308 diameter barrel. Firing an 8mm57 round in a 30/06 chamber will crush the head of the case, loosen the primer and expand the diameter of the flash hole, the crushing of the case head is the cause of the incipient case separation, because? the case body is locked to the chamber when the case head is driven back into the bolt face. It is possible to render your rifle scrap by shooting bullets that are too large in diameter, the practice is a bad habit.
Then there was Hatcher. He knew the case would not stretch .080”, so he moved the shoulder of the chamber forward .080” then fired 30/06 ammo in his new creation, he created the 30/06 Hatcher Modified +.080”. Hatchers cases shortened.
F. Guffey