justashooter in pa
member
- Joined
- May 31, 2009
- Messages
- 358
OP, 4 thou of an inch is not all that stands between you and certain death in the jaws of a killer rabbit that can only be dispatched with an holy hand grenade. 4 thou of an inch is just a target for manufacturers in a wide variety of countries and occupations to agree upon as an acceptance standard.
in experiments done in the late 30's with ww1 surplus ammo from the frankford arsenal that had been declared unserviceable for known excess brittleness it was demonstrated in a series of 1919A4, which have adjustable headspace, that case head seperation does not occur until you get +20 thousandths excess headspace. separation does not reliably occur until you get +30-35 thou. this the result of the controlled firing of tens of thousands of rounds of ammunition at aberdeen. the 1919 was tested in this way to determine the importance of training machine gunners in the fine art of headspace adjustment in field maintinance. it was determined that the issue is less important than the ordnance department examiners originally expected it to be. the 1919 was ideal as the test bed because headspace on them can be easily adjusted and because case head sep does not damage them in any significant manner.
similar experiments were performed with springfield rifles through the alteration of a wide variety of bolts for installation in test rifles, again, in the interest of discovering the importance of quality control in manufacture and maintinance. the results were damned near identical.
this experimentation was also relevant to the selection of brass alloys and heat treatments for use in case forming, as MG generally need brass of specific hardness to avoid case crumpling related feed failures, and need brass of a specific elasticity to ensure that the cases will expand to gas seal the chamber and then relax dimensionally in time for reliable extraction. the alloys selected as suitable for MG use were standardised for the production of all ammo within the application range, and for all ammo intended for other firing platforms in the same chambering, in the interest of uniformity and simplification of logistics.
we can discuss this all week, and i can throw piles of text into this board that is based upon scientific experimentation by highly regarded US ordinance department experts. i have the time. it's just a shame that i have to waste it on a dead horse. knowledge is a good thing if it is deep and wide enuf. if it ain't it's often just a set of handcuffs bunding an otherwise unfettered life.
in experiments done in the late 30's with ww1 surplus ammo from the frankford arsenal that had been declared unserviceable for known excess brittleness it was demonstrated in a series of 1919A4, which have adjustable headspace, that case head seperation does not occur until you get +20 thousandths excess headspace. separation does not reliably occur until you get +30-35 thou. this the result of the controlled firing of tens of thousands of rounds of ammunition at aberdeen. the 1919 was tested in this way to determine the importance of training machine gunners in the fine art of headspace adjustment in field maintinance. it was determined that the issue is less important than the ordnance department examiners originally expected it to be. the 1919 was ideal as the test bed because headspace on them can be easily adjusted and because case head sep does not damage them in any significant manner.
similar experiments were performed with springfield rifles through the alteration of a wide variety of bolts for installation in test rifles, again, in the interest of discovering the importance of quality control in manufacture and maintinance. the results were damned near identical.
this experimentation was also relevant to the selection of brass alloys and heat treatments for use in case forming, as MG generally need brass of specific hardness to avoid case crumpling related feed failures, and need brass of a specific elasticity to ensure that the cases will expand to gas seal the chamber and then relax dimensionally in time for reliable extraction. the alloys selected as suitable for MG use were standardised for the production of all ammo within the application range, and for all ammo intended for other firing platforms in the same chambering, in the interest of uniformity and simplification of logistics.
we can discuss this all week, and i can throw piles of text into this board that is based upon scientific experimentation by highly regarded US ordinance department experts. i have the time. it's just a shame that i have to waste it on a dead horse. knowledge is a good thing if it is deep and wide enuf. if it ain't it's often just a set of handcuffs bunding an otherwise unfettered life.
