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Primers and Fuses
When the gun was loaded, and ready to be fired, the #4 man of the gun crew would insert a friction primer into the vent, attach the hook of the lanyard to the loop of the primer, back away the 12 feet that the length of the cord was and wait for the command to fire given by the gunner. Primers were most often made of a long and a short copper tube, soldered together at right angles. The longer tube was filled with gunpowder and sealed at the bottom with wax, and went into the vent. On the top, the shorter tube was filled with a friction mixture, and a twisted wire was inserted into it, the end of which formed a loop. When the wire was pulled through the friction mixture, the powder was ignited, shooting a flame down into the powder bag firing the gun.
The most common type of time fuses were made of paper cylinders packed with a slow burning powder. There were markings for shortening the burning time marked on the fuses (there were also "fuse measures", a board with a groove for the fuse to sit in, with more accurate graduations). When the gunner established the range to the target, the #6 man would give him the corresponding elevation to use (from the Table of Fire glued inside the limber chest), and cut the fuse to the length required for the time of flight. The fuse, cut to the correct length, would be inserted into wooden or metallic fuse plugs in the fuse hole of the projectile. For consistency, starting in late 1862, the Union had all paper time fuses manufactured at the Frankford Arsenal. Confederate fuses had to be made at a variety of establishments to supply the need, and therefore varied in consistency. The Bormann time fuse was made of metal which screwed into the fuse hole of the ordnance. A hole was punched into the top at a mark corresponding to the length of time wanted. This was more convenient, but not more accurate, and there are existing specimens of Borman time fuses which had been drilled out so that a paper fuse could be used. In both cases, the fuse was ignited by the flame of the propellant charge.
Rifled shells which were fitted with paper fuses sometimes did not have the fuse ignited by the propellant charge. There are some designs of rifled shell and case which had flame grooves up the side of the projectile so that the flame could ignite the fuse before the band was flared into the rifling. Projectiles could also be fitted with percussion or concussion fuses, but these were not as reliable. Percussion fuses had a movable piece with a cone, onto which a percussion cap was placed. When the shell hit, the slider was thrown forward, detonating the cap against the anvil fixed in the fuse. This design didn't work reliably if the slider got cocked, or if the shell hit a glancing blow, not giving enough force to fire the cap. Concussion fuses were designed to go off upon hitting at any angle, but these were unpredictable and dangerous. There were stories of troops being hit by shells fired by their own side which burst prematurely, and that no doubt happened. Many times it was the sabot, a piece of the rifling band or just a piece which broke off the shell as the cannon fired which struck those troops. Many recovered Parrott projectiles have pieces broken off at the base, attributed to the force of being fired."
Taken from a really neat site that I think answers most artillery questions.
http://www.cwartillery.com/FA/FA.html