Impressed Action Marks- FirearmsID.com (2024)

Firing pinimpressions also can be found on live cartridges. One of those fewexceptions I mentioned earlier. In some cases, the firing pin may miss theprimer of a cartridge or fail to strike the primer of a cartridge withsufficient force for it to discharge. The cartridge may also misfire dueto a contaminated or deteriorated primer compound. For whatever reason,the result will be the presence of a firing pin impression on the cartridge caseof a live cartridge. This could be significant if the cartridge is say,left at the scene or found at a suspect's house. The comparison imagebelow shows light firing pin impressions on an evidence cartridge case (left)and a test standard from a suspected firearm (right).

Breech Marks

By far the mostcommon impressed action marks on cartridge cases are breech marks.Most fired cartridge cases are identified as having been fired by a specificfirearm through the identification of breech marks.

Very highpressures are generated within a firearm when a cartridge is discharged. These pressuresforce the bullet from the cartridge case and down the barrel at very highvelocities. When a firearm is discharged, the shooter will feel the firearmjump rearward. This rearward movement of the firearm is called recoil.Recoil is for the most part caused by the cartridge case movingrearward as an opposite reaction to the pressures generated toforce the bullet down the barrel.

When the head orbase of the cartridge case moves rearward, it strikes what is called the breechface of the firearm. The image below shows the breech face of a 12GAUGE, single-shot shotgun.

The breech facerests against the head of the cartridge case and holds the cartridge case in thechamber of the firearm. When the head of a cartridge case slams againstthe breech face, the negative impression of any imperfections in the breech faceare stamped into either the primer of the cartridge case or the cartridge caseitself. The image below shows the primer of a shotshell fired in the aboveshotgun.

Breech marks comein various forms. Those seen above are called parallel breech marks.Obviously, because the marks are a series of parallel lines.

Another form ofbreech marks are circular breech marks like those seen in the comparison imagebelow.

Breech marks canalso show no obvious pattern. They may have a stippled or mottledappearance as seen below.

Ejector Marks

Now back to ejectormarks. Ejector marks are sometimes created when cartridges orcartridge cases are ejected from the action of a firearm. Ejector markscan be either striated or impressed but the impressed ejector marks not only canbe used to identify a cartridge case as having passed through a firearm's actionthey can also be an indication that the cartridge case was fired in thefirearm. Ejector marks like those seen below could only be reproduced whenthe cartridge cases were fired in the firearm and not by simply hand chamberingand ejecting a live cartridge.

Additionalexamples of cartridge case comparisons can be seen in the imagegalleries.