Pressures, Case Strength and Back Thrust

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One of the most important developments in firearms history was the brass cartridge case that first came onto the scene just before the Civil War. In 1856 a dentist named Maynard patented a brass cartridge case that would expand when fired and seal the rifle chamber to close off any escape of powder gases. This forced all pressure to push behind the bullet and send it out the barrel with the best velocity. Sealing of the chamber was a major step in the development of breech loading rifles. Prior to that, all breech loaders spit a lot of fire and brimstone out the rear of the action into the shooter's face.... They were not any too popular in those days.... Read More...

This is a thread for discussion of the article, Pressures, Case Strength and Back Thrust, By Bob Jourdan. Here you can ask questions or make comments about the article
 

jmden

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Nov 2, 2003
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Washington State
Great read on backthrust/chamber friction related to case dimensions and geometry, Len. Thanks. I was thinking about this 2-3 yrs ago and wondered how dry/clean my chamber and cases were. Started swabbing the chamber with acetone as a last rifle cleaning step to completely clean/dry it out before shooting and giving brass walls a quick wipe as well as a last step before storage in the ammo box. The theory was to create more chamber wall friction and less backthrust...who knows.
 

fj40mojo

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Jul 25, 2009
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Salmon, Idaho
Good read Bill,
I was excited when I saw this article and your name along with it. I'm very interested in the 6.5x55 BJAI. How does it compare to say the 6.5-284? Would you consider it to be a worth while modification to a 6.5x55 rifle specifically built on a '98 Mauser action. I'm having a great time with my Swede but case life is lacking and I'm considering recutting the chamber to your Ackleyized cartridge.
 

Bob the nailer

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Dec 9, 2009
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Michigan
Bob,
Great job on the article! always enjoy your work, I built a B.J.A.I. 6.5x55 some years back on a M96 Swede action and never regreted it. Oh yea I picked up a M96 Swede 22br "tight neck" from Bob White ( Built by "Bob Jourdan" you did a fine job machining that one). RL15 and 50 grn noslers are the one hole recipe there, Thanks again for some great articles.



Bob
 

ken snyder

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Jul 26, 2010
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420
Maybe someone has an answer. one of my wildcats is being confusing. I used a .375 R.UM. for the parent brass and made a cartridge that is similar to the .375 Dakota. Its inspiration was to make a longer version of a W.S.M. with .375 diameter bullets. Very little taper and tight headspacing. My concern is that I (QUESTION?) by design eliminated case stretching as one of the common pressure indicators. I honestly do not know if ease of extraction and fired case measurements will begin to show signs of overpressure before a critical loading is reached. -- any ideas?
 

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