No. Exit wounds are frequently larger than entrance wounds, but the reverse and near-equal outcomes occur in a substantial minority of cases. In civilian autopsy series, exits are larger in roughly 60 to 80 percent of through-and-through gunshot cases; contact and near-contact shots, hollow-point deformation, and shotgun injuries break the pattern entirely. Entrance size is driven by projectile diameter and skin elasticity; exit size is driven by yaw, fragmentation, and energy deposited inside tissue—not by which side of the body the bullet crossed.
The mechanism: why exit wounds usually enlarge
A bullet entering skin pushes tissue ahead of it and stretches the elastic fibers before they tear. Skin is tough and highly elastic, so the entrance hole tends to recoil to a diameter close to the bullet's own caliber—often 10 to 20 percent smaller than the projectile itself. The wound you measure at autopsy is smaller than the path the bullet actually carved.
On exit, the dynamics reverse. By the time the projectile reaches the far side, it has lost stability. It has begun to yaw (tumble) or has already mushroomed and fragmented. A tumbling bullet presents its side rather than its nose, so it punches a larger hole. Temporary cavitation—the radial stretch cavity that balloons outward behind the bullet—pushes tissue explosively against the exit surface from the inside. That internal pressure can blow out a ragged, everted wound larger than anything the bullet's diameter would predict.
In plain terms: the entrance is a puncture; the exit is often a blowout from the inside. The bullet does not simply "push through"—it destabilizes, and the destabilized projectile plus radial pressure does the extra damage at the far wall.
Quantified comparison: entrance versus exit dimensions
The table below summarizes typical patterns drawn from forensic pathology literature. These are ranges, not rules—tissue type dominates.
| Variable | Entrance wound | Exit wound |
|---|---|---|
| Typical diameter vs. bullet caliber | 10–20% smaller (skin recoil) | 1.5–4x caliber in unstable bullets |
| Margin shape | Clean, inverted, abraded ring | Ragged, everted, often split |
| Abrasion collar | Present (contact ring of dirt/powder) | Absent |
| Gunpowder soot/tattooing | Present in contact/near-contact shots | Absent (interior contamination only) |
| Tissue bridging | Minimal | Common in irregular exits |
| Frequency larger than counterpart | Rare when exit is larger | 60–80% of through-and-through civilian cases |
The 60–80 percent figure reflects pooled civilian autopsy experience; it is an estimate, not a registry-verified constant. High-velocity rifle rounds shift the ratio toward larger exits far more reliably than handgun rounds.
Caliber and projectile type: when the pattern flips
Projectile design governs whether the exit enlarges or shrinks. Full metal jacket (FMJ) handgun rounds tend to exit with modest enlargement—often only 1.2 to 1.5 times caliber. Hollow-point and soft-point rounds are engineered to expand, and a mushroomed projectile can produce an exit 2 to 3 times caliber, or fail to exit at all if expansion arrests it.
At the extreme, fragmenting ammunition and high-velocity rifle rounds deposit enormous energy and may generate multiple exit wounds or none, depending on whether the jacket sheds. Shotgun injuries are a separate category: at close range the entire pellet cluster behaves as a single mass, producing a devastating entrance and often no discrete exit at all. Birdshot frequently produces no exit; buckshot and slugs often do, with exits larger than the entrance but variable in number.
A counterintuitive correction: the "exit is always bigger" rule is taught because it is common, not because it is reliable. Forensic texts explicitly warn that wound size cannot be used to determine direction of fire in isolation.
Edge cases: contact wounds, bone, and re-entry
Contact and near-contact discharges invert the expected pattern. Gas, soot, and muzzle blast are forced into the wound track, and the entrance may be stellate (star-shaped), lacerated, and larger than the exit—sometimes dramatically so. A contact wound to the head can produce an entrance larger than a distant exit.
Bone changes everything. A bullet striking the skull or a long bone may fragment, and secondary bone fragments can themselves create exit wounds larger than the original track. Conversely, a bullet that strikes bone and loses velocity may fail to exit, leaving only an entrance. Re-entry wounds—where a projectile passes through one body part and re-enters another—add a third wound type that mimics an exit in appearance.
Timeline: wound evolution after the shot
Wound appearance is not static. Forensic and clinical assessment depends on when the wound is examined, and the same wound looks different at six hours versus three days.
| Time after injury | Entrance appearance | Exit appearance |
|---|---|---|
| 0–1 hour | Sharp margins, fresh abrasion collar | Everted, actively bleeding |
| 6–24 hours | Edges begin to dry, slight swelling | Edema, early fibrin deposition |
| 1–3 days | Yellow-brown drying, crust formation | Granulation begins, margins soften |
| 1–2 weeks | Crust separates, healing edge | Contraction, scar forming |
| 3–6 weeks | Mature scar | Mature scar, often broader |
| Months–years | Fades, may become subtle | Broader, more irregular scar |
In living patients, the entrance is typically the smaller, cleaner wound within the first 24 hours; by weeks, the exit scar often remains visibly broader—a persistent echo of the acute geometry.
Correcting the myths and reading real cases
Three misconceptions recur. First, that exit size proves direction of travel—it cannot, because contact wounds and hollow-point deformation break the rule. Second, that a small entrance means a small bullet or a low-energy round—absolutely not; a small entrance with a massive cavity indicates high energy deposited inside. Third, that the largest wound is the exit—in close-range shotgun and contact injuries, the entrance is often the more destructive.
The professional caveat: wound measurements are descriptive, not diagnostic. A forensic pathologist correlates wound size with track geometry, soot distribution, tissue bridging, and projectile recovery—never wound size alone.
What to actually do: practical wound assessment
For clinicians and first responders, wound size should never drive triage decisions. Treat the patient, not the hole. Concrete actions:
- Assess both entrance and exit for active hemorrhage and apply direct pressure to the more proximal bleeding site first.
- Do not probe or measure a wound in the field; probing can enlarge it and obscure forensic evidence.
- Document wound location, size, and appearance photographically before cleaning, when safe and clinically appropriate.
- Preserve clothing and any projectile fragments for forensic chain of custody in suspected assault cases.
- Assume internal injury severity is independent of external wound size—a small entrance can hide a massive cavity.
- Escalate any gunshot wound involving the torso, neck, or head to trauma surgery regardless of wound dimensions.
Limitations and the state of the evidence
The size relationships described here are population tendencies, not laws. Tissue type—skin versus muscle versus liver—changes the numbers substantially, and no prospective registry cleanly quantifies exit-to-entrance ratios across calibers. Much of the forensic literature is retrospective autopsy series with selection bias. The 60–80 percent range should be read as a working estimate, not a measured constant. Investigators who treat wound size as definitive proof of direction, rather than one clue among many, risk error in both forensic and clinical contexts.