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Old October 24, 2011, 07:04 PM   #9
Slamfire
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Join Date: May 27, 2007
Posts: 5,261
Firearms are not designed taking into account case friction. Lets say you are to design a firearm, what % case friction do you use to weaken your mechanism? Pick a number. What ever number greater than zero that you pick will be wrong because you cannot control the shooting environment. It might be raining when the weapon is fired, the shooter may sneeze on the ammo.

Col Townsend Whelen and General Hatcher are the reason Americans are worried about greasing bullets and oil on cases. In 1921 the Army experienced blowups with national match ammunition the bullets of which were coated in tin. These were called the Tin Can ammo. Instead of focusing on the cold welding between the bullet and the case, which caused a bore obstruction, the Army decided on a cover up. They blame shifted the problem to competitive shooters who were applying grease to their bullets in an attempt to reduce bore fouling.

The Army ran bogus pressure tests, “proved” the only problem was the civilians and greased bullets, banned greased bullets from competition, and created a bogus legacy that has lasted for decades. Col Townsend Whelen was in charge of the development and manufacturing of the Tin Can ammunition. As would be expected from a man who made a very visible mistake but absolutely denied any responsibility for his actions, for the rest of his gunwriting life he constantly warned that greased bullets and oiled cases “dangerously” raised pressures. If you have ever read Hatcher’s Notebook you will also notice how cleverly Hatcher misdirects, obfuscates, and blame shifts the problems to the shooters, not the Army Ordnance Department.

Gunwriters have parroted Hatcher and Whelen for decades. Gunwriters are at best Journalist majors, they don’t have the technical background to understand gun design. They never consider the early mechanisms that used oilers, modern mechanisms that use chamber flutes, externally lubricated bullets (such as .22LR which the entire case is waxed), moly lube bullets, paper hull shotgun shells which are heavily waxed, and in fact they have created derivative myths, such as case friction is necessary not to overload mechanisms. That is where the rough chamber myth came about, which is a bogus as you can get.

I think that came about from P. O. Ackley’s promotions of his Ackley Improved Cartridges by shooting a case in a rifle without a locking lug.

Ackley was taking heat because he was getting high velocities from his improved cartridges, cartridges which were being used in actions not designed for the things. P.O. wanted to show that his speedy cartridges did not increase bolt thrust, and infact as a result of his experiments, claimed they actually reduced bolt thrust. Which was bogus as heck as these improved cartridges actually ran at higher pressures. Higher pressures increases bolt thrust, it does not lessen it.

Read carefully “Yielding of Brass Case Walls in the Chamber A Technical Note”, 30 June 2009 James A. Boatright http://www.thewellguidedbullet.com/m...al_studies.htm .Mr Boatright shows how a 308 case, in a clean chamber, can lock in and hold pressures by itself up to 25K psia.

However once pressures go above 25K psia, the brass case stretches and if not supported, the case head will blow off.

If you notice, P.O. Ackley never conducted his test with a 30-06 or a similar high pressure cartridge which would have blown right out his lug less rifle. Instead ole P.O. was interested in promoting his cartridges and left a very misleading legacy in terms of case friction, load, and chamber roughness.

There are a number of fielded weapon systems that used lubricated cases.

Gentleman, that is a Japanese Nambu Machine gun. And on the top is an oiler. This fielded weapon killed lots of Americans and performed satisfactorily throughout the China/Burma/India theater and the South Pacific.












I have shot lubricated cases for several decades in my M1a’s and Garands. I do this because these mechanisms are hard on cases, stretching them so badly that five reloads is a good rule thumb for cases in this mechanism.

I took one set 22 reloads and never had an indication of case head separations.

What I found in developing loads was that the primers in lubricated cases were rounded, whereas in a dry case, the primers were flattened. Obviously the pressures were the same. I am of the opinion that with dry cases the primer backs out, the case stretches and stuffs the primer back in the pocket. With a lubricated case I think the case and primer both move to the bolt face at the same time. But this is based on a cartridges where I set the shoulder back .003". If your primers are flattened I would suspect high pressure. Or maybe you have created huge headspace in your cartridges. I develop my loads with lubricated cases. When the primers flatten, I know I am near a max load.

Excessive headspace will result in peening. Lubricated cases or dry cases. The dry cases will simply be stretched to the bolt face, lubricated cases will slide. If the headspace is excessive you can expect action peening. That is why it is important to control the headspace of your cartridges and rifles.

I highly recommend you buy a cartridge headspace gage and set up your sizing dies using the thing.

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Last edited by Slamfire; October 24, 2011 at 07:11 PM.
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