When a Shotgun Fires a Sequence of Events Takes Place: After the Hunter Pulls the Trigger, What Is the Next Event?

The next event is the firing pin striking the shotshell's primer, crushing it against the anvil to ignite the priming compound. That tiny spark fires through the flash hole into the powder charge. The burning powder then generates gas that drives the wad and shot down the bore. Pulling the trigger only starts a chain—the shot does not leave until four mechanical steps have already happened inside the shell and chamber.

The trigger-to-primer handoff

A shotgun trigger does not ignite anything. It releases a sear, a hardened steel hook that holds the hammer or striker under spring tension. On a typical break-action gun the hammer has been cocked by the act of opening the action; on a pump or semi-auto a spring-loaded hammer sits cocked behind the bolt. When the sear slips, stored spring energy—on the order of a few foot-pounds—accelerates the hammer or striker toward the receiver's rear face.

The firing pin is the last mechanical link. It is a small steel rod that travels through a channel in the breech face and protrudes only a few thousandths of an inch—commonly around 0.050 to 0.060 inch of protrusion on many designs—just enough to dent the primer. Shotgun primers sit in the center of the shell head, so this is a centerfire system: the pin must strike the primer cup, not the surrounding brass. The pin's protrusion is a design compromise. Too little and the primer dents too shallowly to fire. Too much and pierced primers vent hot gas into the action.

That strike is the answer to the sequence question, and it happens within roughly a millisecond of the sear releasing. Everything the hunter hears afterward is downstream of this one impact.

Inside the shotshell: primer, powder, and the pressure curve

The primer is not a simple spark plug. Its cup holds a small charge of impact-sensitive compound—historically lead styphnate, now often formulations using diazodinitrophenol or similar sensitizers—sandwiched over an anvil. When the firing pin dents the cup, the compound is crushed against the anvil and detonates. This is a true detonation, a supersonic decomposition, and it throws a jet of hot gas and incandescent particles through the flash hole in the shell's head.

That flash ignites the propellant, which is not an explosive but a deflagrating powder: smokeless shotgun powders burn progressively from the surface inward, and their burn rate depends on pressure and temperature. This is the key mechanism most thin explainers miss. The powder does not "explode." It burns faster as pressure rises, which is why the powder charge, the hull volume, and the wad's fit are matched by the manufacturer. A shotshell is a tuned pressure vessel, and the primer's job is to start that burn consistently.

Peak pressure in a 12-gauge target load typically runs in the range of about 10,000 to 11,500 psi under SAAMI voluntary standards, while magnum hunting loads can approach the upper limit the standard sets for the gauge. Those numbers matter because the hull, the head, and the chamber are all designed around them.

The wad and the shot column: what leaves the barrel

As gas pressure builds behind the wad, the wad—a plastic cup with a gas-sealing skirt—accelerates down the bore and pushes the shot column ahead of it. The wad does three jobs at once: it seals gas behind the shot, it cushions the shot against the initial jolt (the "shot start" pressure spike), and in many loads it holds the shot in a tighter cluster for a few feet past the muzzle.

The shot itself is dozens to hundreds of small lead or steel pellets. A typical 12-gauge 1-ounce load of No. 7½ birdshot contains roughly 350 pellets; a 1⅛-ounce field load of No. 6 contains around 250. The pellets are not bonded; they are loose in the cup and begin to spread the instant they leave the muzzle, because each pellet has its own slight velocity and direction variation. That is the physical origin of shot spread—not "the gun spraying," but hundreds of independent projectiles diverging.

Choke constriction at the muzzle controls how much that spread is squeezed. A full choke might hold a dense pattern at 40 yards; a cylinder bore spreads wide for close work.

Timeline: from trigger pull to pellets in flight

The counterintuitive detail: the shot is already gone before the hunter feels the recoil. Recoil is a reaction to the shot and gas leaving the muzzle, so the physical event that "kicks" happens after the projectile has departed. Hunters who flinch are reacting to the sound and the anticipated kick, not to the shot's departure.

What can interrupt the sequence

The chain has several failure points, and each produces a distinct symptom.

Failure to fire with a light primer strike: firing pin protrusion too short, a weak hammer spring, or a dirty firing pin channel. The primer shows a shallow dent. Failure to fire with no dent: broken firing pin, seized striker, or a sear that released but the pin never reached the primer. Hang fire: a delayed ignition, rare with modern primers but possible with contaminated powder or a weak primer. The shot may fire a fraction of a second late—never open the action immediately. Squib load: primer fires but powder fails to ignite, leaving the wad and shot stuck in the bore. The report is a pop, not a boom. Firing again with an obstructed bore can bulge or burst the barrel. Pierced primer: excessive firing pin protrusion or overpressure vents gas into the action, which can erode the breech face. Hull failure: a split or swollen hull can leak gas and change pressure, sometimes dramatically.

Misconceptions worth correcting

The most common error is believing the trigger "fires the shot." It does not; it releases stored energy, and the shot is fired by the primer-powder sequence. A second misconception is that shotgun pellets travel as a single mass. They do not; the pattern is a statistical distribution, and the "spread" is built in from the moment the wad leaves the muzzle. A third is that a misfire means the shell is dead. A light primer strike can leave a live primer that may fire on a second attempt, so treat any unfired shell as live until it is safely disposed of. A fourth: recoil does not push the shot out faster; it is a consequence of the shot leaving.

Practical actions for the hunter

If a shell fails to fire, keep the muzzle pointed in a safe direction for at least 30 seconds before opening the action. This covers the rare hang-fire window. Inspect the primer after a misfire. A deep, centered dent suggests a hard primer or a weak strike; no dent points to a firing pin or sear problem. After any "pop" instead of a "boom," stop, unload, and check the bore for an obstruction before firing again. Clean the firing pin channel and action periodically; fouling and congealed lubricant are common causes of light strikes. Have a gunsmith check firing pin protrusion if misfires recur with known-good ammunition. Store shotshells dry and cool; moisture degrades primers and powder and can cause hang fires.

The safety stakes are real: a bore obstruction or a hang fire mishandled can cause injury or destroy the gun. The sequence is short—milliseconds—but the consequences of interrupting it carelessly are not.

Limits of what this explains

This article describes the mechanical and chemical sequence in general terms. It does not cover gun-specific tolerances, which vary by make and model and should be checked against the manufacturer's specifications. Pressure figures cited are voluntary industry standards, not guarantees for any individual shell, and handloading can push far outside them. Shot counts and pellet counts vary with load data and should be taken from the shell's published specification, not from this overview. For any question about a specific firearm's condition, headspace, or firing pin geometry, consult a qualified gunsmith or the manufacturer. Nothing here is a substitute for hands-on safety training and range supervision.