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Firing Sequence from when Trigger is Pulled & Hammer Hits Firing Pin to the Bullet Exiting the Barrel

There is mechanics and science involved when shooting firearms. Many people do not realize what is involved in firing a gun once the trigger is pulled. Covered in the basic parts; interior, exterior and terminal are the science of ballistics. What happens inside the gun when a shooter pulls the trigger simply describes interior ballistics. The sear releases the hammer or the striker, also known as a firing pin. When this happens, it initiates a complex but predictable chain of events. This is known as a firing sequence. Today, we at Shooting Range Industries would like to continue on the basic fundamentals of firing a gun.

Firing Sequence

Below are the basics of the firing sequence.
1) When the trigger is pulled, the hammer rotates forward until it hits the firing pin, driving it forward. If there is no hammer, the striker, or firing pin, moves forward alternately.
2) Just before crushing the priming compound inside against the anvil underneath, the tip of the firing pin strikes the primer cup, deforming it.
3) The priming compound explodes, which sends hot, rapidly expanding gas through the flash hole and into the case. To ignite the propellant, this gas rapidly raises the temperature and pressure inside the cartridge case.
4) While the propellant burns, it generates hot, expanding gas at a temperature of about 5,600 degrees Fahrenheit. Inside the cartridge case, the pressure quickly rises to peak levels up to 62,000 PSI (pounds per square inch). Creating a seal, the prevents hot gas from escaping to the rear, the increasing pressure irons the cartridge case sidewalls outward against the chamber walls.
5) Allowing the expanding propellant gases to accelerate it down the bore, at shot-start pressure, normally 2,000-10,000 PSI, the bullet overcomes case neck tension.
6) The bullet contacts the rifling and engraves, after traveling a short distance in the chamber throat. The rifling lands grip the bullet’s surface, imparting spin as the bullet accelerates down the bore. The bullet breaks the sound barrier about 1/3 of the way down the barrel.
7) Internal volume increases as the bullet accelerates farther down the barrel, causing the chamber pressure to begin to drop. Progressive burning of the propellant offsets the pressure drop to some extent but does not prevent it.
8) When the bullet clears the muzzle, a jet of hot, high-velocity propellant gas, still at 10 to 30 percent of peak chamber pressure, is released. The gas compresses the air surrounding the muzzle as the gas jet escapes, which creates the loud report.
9) The pressure inside the barrel and chamber will drop fast back to ambient levels, this grants the cartridge case sidewalls to spring back from the chamber walls for extraction. Generally, from firing pin to release to the bullet exiting the barrel is measured in milliseconds.

Custom Shooting Ranges for Firearm Practice & Training

When it comes to firearms, the mechanics may seem simple, but a complex series of events that happens in milliseconds. Though many shoot recreationally, it is important to ensure safety measures are in place when storing, handling, and shooting your firearms. Shooting Range Industries designs and builds portable custom shooting ranges so that you can safely and conveniently practice and train with your guns. Call us to learn more today!

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