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Quentin Que Smith
Que Smith is a life member of the National Rifle Association, and a certified instructor in basic handgun, personal protection, and firearms safety. Que is a Glock and Beretta armorer and a Glock instructor. He is well known for his accomplishments in marksmanship, and his expertise in guns and gun handling. You may contact Que at Que Gun Emporium (316) 744-7340, or by e-mail: qsmith@cox.net
Guns, Firearms & Ammunition
2003-04-01 11:23:00
What happens upon firing?
ANSWER:  In order to answer your question adequately, we need to talk about each component. Each component has a specific job to perform when the round is fired. Let's say a round is placed in a gun, and the gun fired. Whatever mechanisms are employed inside the gun, the gun's firing pin strikes the round's primer. The primer ignites, sending an intense flame through a hole in the base of the metallic cartridge case. The primer's flame is used to ignite the powder contained inside the cartridge case. The burning powder builds up pressure inside the cartridge case, and the bullet is pushed from the end of the cartridge case into the gun's barrel. After a trip down the gun's barrel, the bullet flies through the air and strikes its target. Now that we have an approximate understanding of what each component does, let's take a more detailed look at each component. This month we will discuss the Primer. There are two styles of primers available today: Centerfire and Rimfire. I will only discuss Centerfire primers. Centerfire primers consist of three separate subcomponents: primer cup, priming compound, and primer anvil. These subcomponents are assembled as purchased, you do not have to assemble the subcomponents yourself. The primer cup is cylindrical, with one end open and the other enclosed. The open end is where the primer anvil is placed, with the priming compound between the two. The primer anvil has an interesting shape, one perhaps best observed (from an already fired primer, for safety) rather than described. The primer anvil's shape is basically a disc with the center raised so it is adjacent to the priming compound. The priming compound is designed to be shock/crush sensitive, and is an explosive mixture. Recently I have seen information stating there is a foil/paper cover between the anvil and priming compound. As I have no intention of taking apart a live primer, I will take this on faith and simply pass along the information. Handle primers with care. The primer is assembled into the metallic cartridge case so the anvil end (the open end) faces the hole in the metallic cartridge case (called the "flash hole"), and the closed end of the primer cup is somewhat beneath the level of the bottom of the metallic cartridge case. This is so that the primer only ignites when the gun's firing pin strikes it, rather than simply by bluntly striking the base of the cartridge. An example of such blunt impact might be dropping the cartridge on a concrete floor, or when the cartridge is slammed into position by a self-loading gun. Handloaders wishing to keep their current complement of fingers and eyes will carefully check their primer levels. When the gun's firing pin strikes the primer cup's closed end, it indents the primer cup. When the primer cup is deformed, it crushes the priming compound between the priming cup and the primer's anvil. This ignites the priming compound, which as we said earlier sends a flame through the flash hole in the metallic cartridge case. Once a primer is fired, it is not reused. Fired primers are a good source of information regarding the pressure of the assembled cartridge. Primers which appear flattened are a good indication of high pressure, and mean you should not increase pressure any further (and possibly even reduce pressure). A knowledgeable, experienced reloader should be consulted for practical advice in this matter. There are four sizes of primer: small pistol, large pistol, small rifle, and large rifle. Primers also come in standard and magnum strength. Be sure to use the correct type of primer as recommended by your reloading data source. Never switch to another strength (or even change manufacturer) of primer when working with anything besides starting loads. Or put another way, if you are going to change primer vendors or switch to a magnum primer, be sure to work the load up again from the starting load. Magnum primers are not necessarily required for "magnum" cartridges. Magnum refers (in this case) to the strength of the flame produced by the primer. Some military loaded ammunition will have primers that are "crimped", meaning the metallic cartridge case has been somewhat reshaped to tightly hold the primer. I believe the crimp is to prevent the primer from backing out under high pressure. Special tools are available for removing crimp in primers. Some primer manufacturers: CCI, Federal, Remington, and Winchester-Western.  Next time we will talk about ‘powder’ and its role in the firing of a round.
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