Downloaded from https://www.everyspec.com - - -11415-41012 OWAU The firing pin alignment with the primea andth 0.079-0.005 WAN. surface finish of the pin will affect the sensitivity - -of a stab initiator. Other consdertions of im. portmce pertan dirctly to the primer and as discussed in par. 4-3. Generally, the primer spe fications indicate the details of a flring pin and holder. A typical stab detonator i shown in Fig. 0.140.0 .4-.2 4-4(A). (4Stab Pin for Fuze,, M5.57 3-3 INITIATION BY PERCUSSION SContrary to initiation by stab, the fiing pin w- - 00 -OOO-Qo05 does not puncture the case in percussion initia- . tion. This difference in action is due to primer " -- construction.
In a percussion primer, the explo- o2800I OIAtM sive is backed up by a metal anvil. The firing pin dents the ca and pinches the explosive between 374-0002ce and anvil. The minimum energy of the firing Lo.37_o~oo NAM 04s-Qo1 KEyWAy SPHER. RAO. pin is, therefore, a function of the explosive, its 0.126 wI container, and the supporting stucture. Energy must be applied at a rate sufficient to fracture (B) Percussion Pin for Bomb Pure, M904, the granular structure of the explosive. Inciden- to Initiate M9 Delay Element tally, percussion primers are constructed in "this NOTE:- ALL DIMENSIONS IN INCHES manner to seal the gas. Percussion primers are discussed more fully in par. 4-3.
Typical prime Figure 3-1. Typical Firing Pins are shown in Fig. 4B) and (C. Criteria for percission firing pins have not as yet been refined to the same degree as those for stab pins. However, studies have been made of o the effect of firing pin contour on the sensitivity INCLUO O ANGLE 260-40 0 of specific primers. It was found that a hemi- spherical tip gives greater sensitivity than a fiat 0.004 in.r tip and that there is little effect on primer sensi- tivity as a result of changing tip radius.
A hill in- vestigation of the sensitivity relationship with re- spect to cup, anvil, charge, and pin has indicated that sensitivity variations appear to originatk in the nature of primer cup collapme rather than in FINISH e~the detonation phenomenon itself C ALL OVER A study of the effect of firing pin alignment on primer sensitivity indicates that there is little Figure 3.2. Standard Firing Pin for Stab Initiators effect if the eccentricity is less than 0.02 in. Above this eccentricity, sensitivity decreases of 0.004 in. is specified for the stab pin of rapidly because of primer construction. Sensi. Fuze, M557 (Fig. 3-1). tivity also decreases as the rigidity of the primer (4) Material.
Both steel and aluminum alloys mounting is decreased. are in common use as firing pin materials. Tests indicate a slight sensitivity advantage for steel, 3.3.4 INITIATION BY ADIABATIC COMPRESSION but the difference is not sufficient to rule out aluminum alloys or even other metals. A very simple impact fuze that does not con- (5) Other Criteria. The rear end of the pin tain a firing pin is one that is initiated by a proc- may be shaped in any way convenient for assem- ess called adiabatic compression. Fig. 3-3 llus- bly. Two configurations are shown in Fig. 3-1. trates a small caliber fuze of this type. The 34