Percussion primer, development

A review of the vast amt of work performed in the field of percussion primers reveals what is essentially an empirical approach to the development of both primer designs and priming mixts. It is recognized that a percussion primer must perform two vital functions (1) it must fire , ignite , or otherwise function when provided with the proper mechanical stimulus — a firing pin (with optimum contour to its striking end) and (2) it must perform its other function by which the flame , fire , or output will ignite the proplnt properly so as to provide the projectile with the specified velocity and within... 

Kenney, O.M. Stamm T,B. Johnson, Development of High Temperature Percussion Primer , Remington Arms Co Kept No AB-69-6... 

The hot gases from the percussion primer permeate thru the baffle and initiate the BkPdr delay pellet, which burns under the reproducible pressure conditions which are obtained within the delay element housing, with a delay time of 0.035 sec. When the BkPdr element has burned thru, a spit of flame impinges on a detonator loaded with LA a true detonation develops and progresses successively thru the Tetryl-loaded lead-out, the Tetryl-loaded booster lead-in, the Tetryl-loaded booster and Explosive D (Ammonium Picrate) -loaded main (or bursting) charge of the projectile. 

NOTE 1) As one proceeds down any HE train, the size of the expl elements from the primer to the main chge increases while their sensitivity to initiation decreases 2) As implied in the word "train", each element has two ends and concomitant with this fact has two characteristics, an input characteristic and an output one. For example the percussion primer is tested by drop weight apparatus (such as represented in Fig 9-1, p 9-5 of Ref 23), to determine its input end characteristics, while its output end characteristic is given by the number of calories of heat developed on the firing and which appears in its output flame. The LA detonator is characterized on its input end by flame sen-... 

Other methods for measuring output of percussion primers include (1) method developed at PicArsn in 1946, based on measurement of the primer light output by means of a photoelectric tube and a cathode ray oscillograph (PAChemLabRepts 114842 118810) (2) measurement of output in... 

B.A. Bydal, Percussion Primer Mixes , Ordnance, Vol LVI, No 309, 230-33 (Nov-Dec 1971) (A review of the history of initiating explosives from their discovery early in the seventeenth century up to the development of today s safer noncorrosive, nonmercuric mixes)... 

Ignition of the propellant was a major problem from the introduction of gunpowder in the early fourteenth century until the development of a percussion primer by a Scottish clergyman, the Reverend Alexander John Forsyth,... 

In 1805 the Reverend Alexander Forsyth used mercury fulminate as the basis of his primer composition, and from this time the percussion system developed into today s highly reliable, universally used, percussion primer compositions. This development which started in 1805 still continues today, and manufacturers are very reluctant to release details of their compositions. 

A review of the vast amt of work performed in the field of percussion primers reveals what is essentially an empirical approach to the development of both primer designs and priming mixts. 

While increased sensitivity can make nano-thermites more dangerous to handle, the increased friction or impact sensitivity is also beneficial in some practical applications such as percussion primers. However some nano-thermites have increased ESD sensitivity, which has no current practical apphcation and is only a safety hazard. For example, a Bi203/Al nano-thermite has sufficient impact and friction sensitivity to be considered for use in ammunition primers, however it has an ESD sensitivity of 0.125 gj (40 nm Bi203, 41 nm Al). This is a static potential, which is easily achieved by the human body. This makes handling hazardous, especially since the Bi203/Al thermite has a combustion velocity of over 750 m/s which means that this thermite explodes rather than bums. The increased ESD sensitivity of nano vs. micron composites is believed to be the result of the increased ability of high surface areas to develop charges. 

Sheffield, Encycl of Expls, Vol 4(1969)) pp D753-R to D756-L (Brief description of matchr lock, wheel-lock, flintlock and percussion-lock in Section entitled "History of Development of Military Detonators, Igniters, Primers and Other Initiating Devices )... 

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