What a Match Is to Your Cigar 



So is a primer to its giant shell 



NOWADAYS 

 every one 

 knows what a 

 shell looks like, and 

 some of us can even 

 differentiate between 

 a high-explosive shell 

 and a shrapnel. We 

 are quite familiar with 

 shells of small caliber 

 and read constantly 

 of the destructiveness of the large 15- 

 inch and 16-inch shells. There is nothing 

 novel to us in the general appearance of 

 a shell such as shown here. We 

 know that in the base of that shell is 

 a little disk which corresponds with 

 the cap in the cartridge-case of our 

 own shot-gun. This is the primer, 

 and while its existence is taken for 

 granted, its mechanism and ~ 



operation are less copper . s^ 



It is the primer 

 which ignites the charge in the 

 cartridge case to drive the pro- 

 jectile from the gun on its mission 

 of destruction. Its function is 

 similar to that of the cap in the 

 base of a shot-gun cartridge, but 

 the duties devolving upon the 

 primer of an artillery shell are 

 more complex. The primer has 

 not only to fire the powder charge 

 in the cartridge case, but also to 

 prevent any of the propelling 

 gases from escaping back into the 

 breech of the gun. 



The primer is composed of six 

 parts — not including the explo- 

 sives used — each one of which has 

 a distinct and definite duty to 

 perform. First, there is the 

 primer body, which houses the 

 operating mechanism and mediums 

 and which screws into the base of 

 the cartridge case. In what may 

 be termed the primer "hub," there 

 is the primer cap which corre- 

 sponds with the cap of a shot-gun 

 cartridge. Next comes the anvil 

 against which the explosive cap 

 has to be driven to ignite the 

 charge. Capping the central hole 



Above: Cra- 

 ter made by 

 giant shell 



of the hub and hold- 

 ing the anvil in place 

 is a tight-fitting plug 

 with several flash 

 holes. Completing 

 the primer is the 

 closing-in disk over 

 which the edges of the 

 primer body are rivet- 

 ed. Within the 

 conical cavity in the 

 anvil base is a small 

 soft brass ball which 

 plays an important 

 and interesting part. 

 A highly explosive and ignitable 

 substance is contained in the 

 primer cap and held in place by a 

 tin-foil disk. This explosive sub- 

 stanceisreadily 

 projectile set off by shock 

 and is driven 

 against the anvil block by the 

 hammer of the gun on firing. 

 The flash created passes through 

 the anvil by way of small flash 

 holes leading through the anvil 

 nose to the cavity in which the 

 soft brass ball is loosely confined, 

 then through the flash holes in the 

 plug, destroying the paper disk 

 \! cemented to 



^N CAR ^|g GE the top of the 

 plug to prevent 

 the powder in the magazine of the 

 primer from working down 

 through the flash holes. On the 

 under side of the closing-in disk 

 is another disk of paper to prevent 

 the escape of the magazine powder 

 charge through its flash slits. The 

 flash transmitted through the 

 anvil and plug from the explosion 

 of the primer cap ignites the 

 powder in the magazine, which, in 

 turn, ignites the pro- 

 pelling charge in the 

 cartridge case proper. 

 primer The flame from the primer 



The primer ignites 

 the charge in the 

 cartridge case to 

 drive the projectile 

 from the gun on its 

 deadly mission 



361 



magazine breaks through 

 this^second paper disk and escapes 

 through the radiating flash-slits in 

 the closing-in disk. 



The explosion of the charge in 



