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Old November 24, 2012, 02:10 PM   #67
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Join Date: May 27, 2007
Posts: 5,075
A good reason your ball ammunition did not have slamfires is due to the work in the early 60's by the military to use less sensitive primers and lighten the firing pin. This is a matter of record:


Primer Sensitivity

Initial Specifications. Ammunition specifications established by the Air Force on 24 January 1963 provided for quality control against cocked, inverted, loose, and nicked primers. The specifications further provided for inspection and test of waterproofing
and the crimp of primers. However, the specifications did not provide for specific limitations on primer sensitivity for 5.56mm ammunition.-

Development. At the first meeting of the Technical Coordinating Committee on 26 March 1963,16 / the Air Force representatives submitted a list of reported ammunition deficiencies, which included "high primers" and "primers too sensitive". It was agreed that Frankford Arsenal would investigate the matter and recommend corrective action.

One of the malfunctions reported by the Air Force was the premature firing of cartridges that occurred upon initial charging of the M16 rifle with a cartridge from the magazine, or upon singleloading of a cartridge directly into the chamber, or when two rounds were fired at one trigger pull during semiautomatic fire.

This malfunction was attributed to "high" or protruding primers, although the tests did not confirm this theory..

However, analysis indicates that if high primers caused the premature firing, the firing should have occurred upon impact of the bolt face with the protruding primer. At this point in the weapon cycle, the bolt head would not. have been rotated to the locked position by action of the cam pin and carrier. Had firing occurred with the bolt in the unlocked position, it would have resulted in a blow back and would not have been undetected. No such disruptions were reported-. Since premature firing occurred after bolt-locking, it must have coincided in time with the impact of the bolt carrier against the bolt head. At the instant of impact, the "free floating" firing pin is moving at the velocity of the bolt carrier. The kinetic energy of the pin must be dissipated by such frictional forces as it encounters in the forward movement, and, finally, in impact of the firing pin tip with the primer of the chambered cartridge. This premise was confirmed by the visible indentation appearing on cartridges which were chambered by the mechanism and extracted unfired.

Frankford Arsenal identified test procedures for measuring firing pin energy and recommended limits for primer sensitivity.

These procedures were designed to measure the indent depth of the firing pin upon the primer cup. Tests are conducted by dropping steel balls of known weights from various measured heights upon a device containing a firing pin and a primed case assembly.

Using this procedure and measuring the energy in inch-ounces, Frankford Arsenal was able to develop test data upon which to recommend a lower limit of "none-to-fire" and an upper limit of "all-to-fire".

It recommended that primers be manufactured so that the none-to-fire limit should be not less than 16 inch-ounces of energy and the all-to-fire limit should be not greater than 64 inch-ounces of energy.
Picture from The top firing pin is the early, heavy firing pin.

Primers are not as predictable as we want. Any time there is incidental contact with a primer there is a very small probability, a very very small probability, but finite, that the thing will ignite.

By Eric Pfeiffer, Yahoo! News | The Sideshow – Tue, Jun 12, 2012

A Pennsylvania woman was shot in the leg while shopping at a local department store on Tuesday. But in a nearly unbelievable twist, no gun was involved. Apparently, the woman was carrying the bullet in her purse, when it mysteriously exploded.

"She did not have a gun in her purse or on her," Montoursville Deputy Police Chief Jason Bentley told the Williamsport Sun-Gazette. Bentley said the woman, whose name has not been released to the public, "was not aware" she was carrying two or three bullets inside her purse at the time of the accident.

The 56-year-old woman was taken to a local hospital and was eventually discharged. In fact, the woman initially declined medical treatment, only heading to the Williamsport Regional Medical Center after her son reportedly encouraged her to do so.

"Something must of hit the primer of one of the bullets," Bentley said. "The bullet stayed in the purse, but its casing put a hole in the purse and caused a minor leg wound."

Bullets exploding outside of a gun are a rare occurrence but are not entirely unprecedented. In March, a bullet being used as evidence in a court case exploded in a bag and shot 20 feet across a courtroom. No one was hurt in the incident. It was surmised that the bullet exploded after its tip bounced against another bullet tip in the same evidence bag, according to the Telegram & Gazette.
If I'm not shooting, I'm reloading.
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