How Much Can a Gunshot Injury Say About the Gun Used?

Gunshot injuries can reveal a lot of information, but don't expect miracles. (Shutterstock photo)

Gunshot injuries can reveal a lot of information, but don’t expect miracles. (Shutterstock photo)

TLDR: It depends, but it’s probably not as much as you think.

Howdunit Forensics DP LyleFull disclosure: I’m not a forensic scientist. I can’t hold a candle to books like Dr. D.P. Lyle’s Howdunit Forensics (Writer’s Digest Books) unless I’m burning it as part of a book ban, and I gave those up years ago.

Regardless, I’ve served as a resource for journalists working on stories involving firearms and crime, including homicide. In one instance from last year, I provided commentary on autopsy reports from a notorious shootout in Texas about the firearms used. The experience highlighted how much and how little a gunshot injury can reveal about the firearm used.

Download: Read a Real Autopsy Report for Yourself

Read an Autopsy Report

Click to download the autopsy report (PDF).

You can read the same autopsy report I did for that shootout by downloading it here. (It’s public record.) It’s a good example of the kind of information that a medical examiner would glean from a gunshot wound during an autopsy.

Prepare to be underwhelmed. This isn’t the stuff of TV cop shows. It’s actually pretty basic, probably because it isn’t a medical examiner’s job to solve cases and assign guilt. Sorry, CSI.

P.S. There aren’t any gory pictures in that report. It’s safe for work.

Yes: The (General) Type of Firearm Used

Based on the entry and exit wounds, it’s fairly straightforward to determine if the firearm was a rifle or handgun, or shotgun. Rifles and handguns fire single projectiles, while shotguns fire multiple BBs (when they’re not firing slugs, which actually is a single projectile).

Keep in mind we’re talking about a firearm type in the most general sense. Rifles, handguns and shotguns are large categories in their own rights.

No: The Exact Model of the Firearm Used

Sure, it might be possible for a clue to point to a particular model of firearm, but I’d bet that’s the exception, not the rule. It’s just a gunshot wound, not a fingerprint.

Maybe: The Caliber of the Firearm Used

At least for rifles and handguns, measuring the diameter of the entry wound will reveal something about the caliber of the firearm.

Remember that “caliber” refers to the diameter of the bullet. A .22 caliber bullet has a diameter of 22/100 inches, while a 9mm bullet has a diameter of 9mm.

When noting a small entry wound, it’s reasonable to suspect a small caliber. A medium-sized entry wound equals a medium caliber. You get the drift.

This is exactly how that autopsy report went about determining caliber. It cited small- and medium-caliber firearms as the source of certain gunshot injuries.

That applies for entry wounds, though. The exit wound (where the projectile leaves the target) will be much larger because of the way bullets mushroom upon impact.

Caliber, though, doesn’t mean as much as it might seem. What qualifies as small? What counts as medium? While there are guides to those ranges in the firearms world, I’ve found they don’t always match up with how the medical community views things. Heck, some of the people I know personally don’t agree with my own definition.

Maybe: Distance of Firearm

A literal smoking gun isn't as helpful nowadays as it was back in the dirty days of blackpowder. (Shutterstock photo)

A literal smoking gun isn’t as helpful nowadays as it was back in the dirty days of blackpowder. (Shutterstock photo)

The autopsy report noted a lack of gunshot residue around the injuries, indicating the gun was fired from a distance too far to leave soot or burns on or near the entry wounds.

This is only significant for knowing the gun was fired at greater than point-blank range (i.e. right next to the target). Back when blackpowder ruled the day, the level of powder around a wound was probably more helpful. Blackpowder didn’t burn cleanly, meaning guns spit a lot of powder into the air when fired.

However, this is the era of smokeless gunpowder/propellant. As explained in this post, powders burn much more cleanly, although “smokeless” is a bit of a misnomer. This means less residue around gunshot wounds, making it difficult to gauge distance.

A forensics expert might have more to say, but it’s safe to reason that a lack of gunshot residue on the wound indicates little beyond “greater than point-blank range.” And that isn’t saying much.

Yes: Type of Ammunition

Here’s where some definite conclusions can be made.

Hollow-point bullets aren't designed to pass through targets because they break apart upon impact. These hollow points have a copper jacket, which means they penetrate a little farther into a target before breaking apart. (Shutterstock photo)

Hollow-point bullets aren’t designed to pass through targets because they break apart upon impact. These hollow points have a copper jacket, which means they penetrate a little farther into a target before breaking apart. (Shutterstock photo)

If an intact bullet can be recovered from inside the body, bingo. It may be possible to identify not only the caliber, but the kind of cartridge used as well. If you’re familiar with microstamping (i.e. a sort of ballistic fingerprinting), remember that information is only stamped on the primer (a part of the casing), not the bullet itself.

If an intact bullet cannot be recovered in the body and left through an exit wound, you know you’re not dealing with a hollow-point bullet. Hollow points break into pieces upon impact.

If shards of a bullet are recovered inside the body, it’s a good bet the shooter used hollow-point bullets. They bust apart after hitting a target, and it’s not likely there would be an exit wound. If, as in the case of the autopsy report, there are also fragments of other metals, such as copper, it’s likely the shooter used jacketed hollow-point bullets. These are explained in more detail here.

If several BBs are recovered from inside the body, it’s pretty obvious a shotgun was used.

Yes: Trajectory

Tracing a projectile’s flight is as easy as connecting the dots between the entry wound, the internal wounds and the exit wounds. How this relates to the crime scene requires a level of analysis I can’t provide here.

Final Note

There’s plenty more ground to cover on this topic. What I’ve described is only a primer. I highly recommend checking out a dedicated forensics resource, such as Howdunit Forensics, for a more in-depth look.

Get the Book

The Writers Guide to WeaponsThe Writer’s Guide to Weapons: A Practical Reference for Using Firearms and Knives in Fiction (Writer’s Digest Books) comes with everything but the ammo. Pick up a print or digital copy from these fine retailers:

8 thoughts on “How Much Can a Gunshot Injury Say About the Gun Used?

  1. And I here I thought: Handful of scorched and crispy hints at fireball, single corpse with no visible wound hints at magic missile… Oh, damn. Your hint is already extensive, and rightfully so, as it reminds us of the science ‘behind the curtain’.

    I join Sue Coletta with the ‘Impressive!’, as it does certainly point crime-fiction-authors into a helpful and very professional direction!

    Liked by 1 person

  2. Pingback: Gunshot Wounds and What They Tell Us | DV Berkom Books

  3. Actually, most jacketed hollow-point bullets that are well designed for their purpose/intended target should not break up into fragments in the body of a victim. A good hollow-point, extracted from the “target organism” should be in one piece–displaying a sort of classic mushroom shape. The purpose of this design is to increase the effective diameter of the projectile once it hits: for example, a bullet from a .357 might well expand to a diameter of .450″, more or less. With the effective diameter increase comes an increase in the amount of damage that is done to the soft tissues of the target, and a corresponding increase in the ability of the ammunition to incapacitate the person or animal hit by the bullet..

    That being said, however, there are some bullets (such as those loaded in Glaser Safety Ammo) which are indeed designed to break up in the target–thus reducing the chance of collateral damage on the far side of the target.


    • We’ll have to disagree on this one, Ralph. You’re right that hollow-points are designed to mushroom beyond the typical diameter of standard, ball ammo. More mushrooming means a higher likelihood of breaking apart, which is often the case. This isn’t limited to one brand, and it’s why hollow-points in general are used by law enforcement. They aren’t often used for hunting (if they’re allowed by law at all), because of the way they break apart, increasing the chance of turning good meat into hamburger.

      I’ll add to that that hollow-points aren’t inherently more or less damaging than other types of ammunition. What matters is the way it’s used and under what circumstances.


      • Sorry, Ben, but as great as the overall information presented here is, I have to side with Ralph on the jacketed hollow point issue. I’m a retired cop, spent half my career as s detective working violent crime, have also been to autopsies, was a firearms instructor, have seen bullet wounds and attended an FBI ballistics school. Hunting laws nearly always REQUIRE expanding ammunition because they transfer energy far better and have a greater chance of bringing down the game animal quickly. The expanding action of a hollow point (especially in pistols as even “powerful” pistols pale in comparison to rifle ballistics) is not so much to create a bigger wound via a bigger bullet (a .357 @ .356″ or about 9mm expanding to .45 caliber or about 11.5 mm is only 2.5mm larger in diameter so even “really big” expansion is not all that big in relation to the human body). Further, evidence shows that there is often a pressure wave in front of the bullet that moves tissue a bit so it really isn’t that much more likely to strike anything vital than a non-expanding round. The main purpose of expanding ammunition is to create a parachute effect on the bullet its self, slowing it down. When that occurs, the kinetic energy of the bullet has to go somewhere and is bled off into the surrounding body tissue. Again, the effects are not always all that significant when discussing handguns (sometimes they are, sometimes not, depending largely on what, exactly is hit and at what velocity), although contact and near-contact shots where the expanding gasses from the muzzle can actually enter the body are a whole ‘nuther topic of messy destruction.

        In a recently published opinion the FBI stated they cannot with any degree of certainty state that expanding ammunition is any better at stopping a human being than is non-expanding ammo, when using common police/military pistol calibers. They could not even find a genuinely significant difference in 9x19mm, .40 S&W, and .45 acp (note they just went back to 9x19mm).

        Most police departments issue JHP (jacketed hollow point) rounds to:
        A: hopefully decrease the number of times a perp has to be shot (the quicker he’s brought down the safer everyone is
        B. to decrease the risk to other citizens and property from bullets that may otherwise pass through the offender or in the case of a miss, ricochet more wildly.
        Please note that even at that, most shootings require multiple “good” hits to bring the offender down, unless the central nervous system is struck.

        Otherwise, excellent information and much appreciated!


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