Bullets can absolutely start fires, and the science behind how they do it is more straightforward than most people assume. When a bullet strikes a hard surface at high speed, the enormous kinetic energy doesn’t just disappear. It converts into heat through the violent deformation and shattering of the bullet, producing fragments that can reach temperatures above 800 °C. Whether those superheated fragments actually ignite surrounding vegetation or material depends on a handful of factors, with bullet composition and environmental conditions topping the list.
How a Bullet Generates Heat on Impact
A rifle bullet can leave the muzzle traveling faster than 900 meters per second. When that bullet slams into a rock, steel plate, or other hard surface, all of that velocity has to go somewhere. Research by the U.S. Forest Service concluded that the kinetic energy of a bullet is transformed into thermal energy through plastic deformation and fracturing caused by the extreme strain rates during impact.1U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. A study of ignition by rifle bullets In plain terms, the bullet gets crushed and torn apart so quickly that the energy has no time to dissipate gradually. Instead, it concentrates as heat in the tiny fragments that spray outward from the point of impact.
Those fragments are not just warm. Thermal infrared video and temperature-sensitive paints used in the same Forest Service experiments showed that bullet fragment temperatures can exceed 800 °C, which is well above the ignition temperature of dry grass, pine needles, and many other common wildland fuels.2Treesearch (USDA Forest Service). A study of ignition by rifle bullets For context, dry grass can ignite at temperatures around 300–400 °C, so a fragment at 800 °C has a comfortable margin to start a fire if it lands in the right fuel.
Why Bullet Composition Changes Everything
Not all bullets are equally dangerous as fire starters, and the difference comes down to what the bullet is made of. The Forest Service ignition study found that bullets containing steel components, whether in the core or the jacket, reliably caused ignitions in dry peat moss fuel beds. Solid copper bullets also proved effective at starting fires. By contrast, traditional lead-core, copper-jacketed bullets caused only a single ignition across the entire set of tests.2Treesearch (USDA Forest Service). A study of ignition by rifle bullets
The reason ties back to what happens during that violent impact. Steel is harder and fractures into larger, hotter fragments that retain enough heat to ignite fuel after landing. Solid copper behaves similarly because it’s tough enough to produce substantial fragments rather than splattering into tiny, rapidly cooling bits. Lead, on the other hand, is soft and has a low melting point. When a lead-core bullet strikes a hard surface, it tends to deform into small particles that cool quickly, shedding their heat before they can light anything on fire. The fragments collected from steel-core and solid copper bullets were physically larger than those from lead-core bullets, and that extra mass helps them stay hot long enough to ignite vegetation.
This distinction matters practically because steel-core ammunition is common in surplus military rounds and some inexpensive imported ammunition. Shooters who buy cheap steel-core or steel-jacketed rounds for target practice are, from a fire-ignition standpoint, using the most hazardous type. The growing popularity of solid copper bullets for hunting, driven by lead-free regulations in some states, introduces a similar but less widely recognized risk.
What You’re Shooting At Matters Too
The bullet alone doesn’t tell the whole story. The target surface plays a critical role in whether an impact generates enough heat and sparking to cause ignition. Hard, non-yielding targets like rocks, steel plates, and concrete force the bullet to deform more violently than softer materials like dirt berms or sand. That more violent deformation means more energy converts to heat in a shorter time, producing hotter fragments.
The Forest Service experiments tested bullets against both steel and granite targets. Ignitions occurred with solid copper bullets striking granite, demonstrating that natural rock formations, not just man-made steel targets, can serve as the hard surface that triggers the process.2Treesearch (USDA Forest Service). A study of ignition by rifle bullets This finding is significant because recreational shooters in the western United States often shoot in rocky terrain where exposed granite, basalt, and other hard rock faces are common. A bullet that misses a paper target and strikes the rocky hillside behind it can produce the same hot fragments as one intentionally fired at a steel plate.
Research on friction sparking from different metal alloys adds another layer. When metals collide, the sparking behavior depends heavily on material properties like hardness, melting point, and thermal conductivity. Tests on various alloys found that softer metals with high thermal conductivity and low melting points, like aluminum and bronze alloys, produced no bright friction sparks even at high velocities. But stainless steel, carbon steel, and titanium alloy all generated bright, energetic particles capable of igniting sensitive dust layers.3ScienceDirect (Elsevier / Fire Safety Journal). Friction spark generation and incendivity of several metal alloys The practical takeaway: a steel-jacketed bullet hitting a steel target is essentially a worst-case combination for spark generation.
The Muzzle End of the Equation
Impact isn’t the only moment a bullet can introduce fire risk. The instant a gun fires, the propellant charge detonates inside the chamber and barrel, producing a brief but intense burst of hot gas, flame, and unburned powder particles that exit the muzzle alongside the bullet. This muzzle blast is hot enough to scorch materials at close range.
Forensic research on point-blank gunshot effects has documented that soot and particles of unburned gunpowder are deposited as additional factors of the shot at close distances.4Theory and Practice of Forensic Science and Criminalistics. Specifics of fire damage to cotton clothing while shooting point-blank at a human torso simulator from a Fort-12RM pistol Those unburned powder particles are still chemically reactive and hot when they leave the barrel. At typical shooting distances of tens or hundreds of meters, the muzzle blast dissipates long before reaching the target, so this is mainly a concern right at the shooter’s position. Dry grass or brush directly in front of, or beneath, the muzzle of a rifle or pistol can receive enough heat and burning particles to ignite, particularly in very dry conditions. Shooters lying prone in dry grass are the highest-risk scenario for muzzle-related ignitions.
The bullet itself also picks up heat before it ever leaves the gun. Barrel-bullet friction and the initial explosion of the propellant both transfer heat to the projectile as it travels down the barrel.5PubMed Central. Temperature Measurement of a Bullet in Flight While this doesn’t raise the bullet’s temperature to wildfire-ignition levels during flight, it means the bullet arrives at the target slightly warmer than ambient, which adds marginally to the thermal budget available during impact.
Exploding Targets Are a Different Beast Entirely
A category of fire risk that deserves separate attention is the use of binary exploding targets, commercially sold products that consist of two chemical components (typically ammonium nitrate and aluminum powder) which are mixed on-site and detonated by a bullet strike. These are used for the dramatic visual and audible feedback they provide at long range, and they introduce fire risk that goes well beyond what a bullet alone can create.
The U.S. Forest Service conducted experiments with 97 exploding targets under different conditions. Tests run in cold, humid weather produced no ignitions. But under warm, dry conditions, ignitions occurred and were positively related to the aluminum concentration in the mixture and to placing the target directly on a straw fuel bed rather than elevating it on a steel pedestal.6Treesearch. Experiments on wildfire ignition by exploding targets The aluminum powder burns at extremely high temperatures during the detonation, and when the target sits directly on dry fuel, the burning aluminum particles shower straight into the ignitable material beneath.
Several western U.S. states and many individual land-management agencies have banned or restricted exploding targets on public land during fire season precisely because of these findings. The risk profile is fundamentally different from a standard bullet impact: instead of small fragments that may or may not land in fuel, an exploding target produces a deliberate detonation that blankets the surrounding area with incendiary material.
How Often Bullets Actually Start Wildfires
Despite the clear physical mechanism, bullet-caused fires remain a small fraction of the overall wildfire picture. An analysis of U.S. agency wildfire records found that among human-caused fires that could be assigned a specific cause, only about 0.2 percent fell into the firearms and explosives use category, totaling roughly 2,200 fires in the dataset.7Fire Safety Journal. Agency records of wildfires caused by firearms use in the United States Of those, half were attributed to military ordnance rather than recreational shooting. About 35 percent were linked to shooting at inert targets, and another 5 percent to exploding targets.
Those numbers might sound reassuringly small, but they can be locally significant. A study of Bureau of Land Management National Conservation Lands found that at one major monument area in the western U.S., 68 percent of fire ignitions were attributed to human activities, and firearms and explosives use accounted for 34 percent of those ignitions, making it the leading human cause at that site.8PubMed. Recreation and firearms use as an emerging wildfire risk on western United States National Conservation Lands In arid, heavily used public lands where recreational shooting is popular, bullets are not a trivial fire source. The national-scale numbers dilute the reality in the specific landscapes where the problem concentrates.
The seasonal pattern reinforces this. Over 90 percent of shooting-caused fires of significant size in the western states ignited during May through October, the warm and dry months when vegetation is most flammable.9ScienceDirect (Elsevier / Fire Safety Journal). Agency records of wildfires caused by firearms use in the United States The same shot that would be harmless in January when the ground is wet or snow-covered becomes a fire starter in July when the grass is cured and the relative humidity is low.
Reducing the Risk If You Shoot Outdoors
Understanding the mechanisms makes practical prevention fairly intuitive. The variables within a shooter’s control are ammunition choice, target material, target placement, shooting location, and timing.
- Ammunition: Standard lead-core, copper-jacketed rounds are far less likely to cause ignition than steel-core, steel-jacketed, or solid copper bullets. If you’re shooting during fire season in dry country, this is the single biggest lever you can pull.
- Target surface: Shooting into a dirt berm or sand backstop absorbs the bullet’s energy more gradually and produces less extreme fragment temperatures than shooting at steel plates, rocks, or concrete. If you use steel targets, keeping the surrounding area clear of dry vegetation creates a buffer zone.
- Exploding targets: Avoid them entirely in dry conditions. The research is clear that warm, dry weather combined with ground-level placement on dry fuel is a recipe for ignition.
- Muzzle area: Clear dry grass and brush from the area directly in front of and beneath the muzzle, especially when shooting from a bench or prone position.
- Season and weather: The overwhelming majority of shooting-caused wildfires happen during warm, dry months. Checking local fire conditions and adhering to fire restrictions on public land isn’t just a legal formality.
Some public land agencies in the western U.S. have implemented seasonal shooting closures or designated shooting areas with cleared ground specifically to address this risk. These measures tend to concentrate in areas where the combination of heavy recreational use and dry vegetation has produced repeated ignitions.
Why Ricochets and Fragmentation Patterns Are Hard to Predict
One reason bullet-caused fires are difficult to prevent entirely is that the behavior of a bullet on impact is chaotic. The angle of impact, the exact composition and surface texture of whatever the bullet hits, the bullet’s remaining velocity, and its construction all interact to determine whether the bullet shatters into hot fragments, ricochets mostly intact, or buries itself in the surface. Research on bullet ricochet marks in concrete found enough variability across different bullet types and distances that even machine learning models classifying ricochet marks achieved overall accuracy of only about 62–66 percent.10Oxford University Press / PMC. Bullet ricochet mark plan-view morphology in concrete: an experimental assessment of five bullet types and two distances using machine learning If the physical behavior of the impact is that variable, predicting exactly when a given shot will produce enough heat to ignite vegetation is essentially impossible on a shot-by-shot basis.
This unpredictability is why fire prevention in shooting contexts relies on broad risk reduction rather than precise prediction. You can’t know which individual shot will be the one that starts a fire, but you can shift the odds dramatically by controlling the factors that make ignition physically possible. A lead-core bullet hitting a dirt berm in January sits at the extreme low end of ignition probability. A steel-core bullet striking exposed rock in August sits at the opposite end. Most real-world fire starts from firearms occupy the high-risk end of that spectrum, which is why the prevention measures focus there.
Thermal Imaging and What Researchers Actually See
Studying the thermal events during bullet impact requires specialized equipment because everything happens in milliseconds. Researchers have used both pyrometry and high-speed thermographic imaging to capture what goes on during and immediately after a bullet strikes a surface. In one set of experiments, thermographic imaging captured a combustion cloud within a test chamber at multiple time intervals following impact, with most of the thermal activity concentrated in the first few milliseconds.11Measurement. Comparing pyrometry and thermography in ballistic impact experiments
What these images reveal is that bullet impacts produce a brief but intense thermal event. The combustion cloud that forms at the point of impact is not a sustained flame but a fast-moving spray of hot gas and particles that disperses quickly. The window for ignition is narrow: a fragment has to be hot enough and land in fuel that is receptive enough in the fraction of a second before it cools below ignition temperature. This explains why bullet-caused fires don’t happen with every shot, even in high-risk conditions. The physics favor ignition only when several factors align simultaneously: the right bullet material produces large, hot fragments that happen to land in dry, fine fuel before they cool.
The extreme speed of these events also explains why shooters rarely realize they’ve started a fire until smoke becomes visible, which can take several minutes in light fuels. By then, the fire may have spread well beyond the point of origin, making it hard to stomp out. This delay between the triggering shot and visible smoke is one reason outdoor shooting ranges increasingly emphasize having fire-suppression equipment on hand rather than relying on shooters to prevent every possible ignition.