Wet gunpowder won’t explode, but depending on the type and how long it stays wet, it may never work the same way again. Black powder is especially vulnerable to water because its components can dissolve and separate. Modern smokeless powder and factory ammunition hold up better, but moisture still degrades performance over time.
Black Powder Dissolves and Separates
Black powder is a physical mixture of potassium nitrate (saltpeter), charcoal, and sulfur. Potassium nitrate is water-soluble, which is the core problem. When black powder gets wet, the nitrate dissolves into the water and migrates away from the charcoal and sulfur particles it needs to be intimately mixed with. Black powder only burns properly when all three ingredients are blended at a near-molecular level, so even a brief soaking can undo that careful mixing.
If you dry the powder out, the nitrate recrystallizes, but the new crystals are much larger than the originals and no longer evenly distributed through the mixture. The result is powder that still burns, but burns slowly, unevenly, and with heavy residue. Globs of molten material form instead of a clean, fast combustion. For practical purposes, black powder that has been thoroughly soaked is ruined. A light misting on the surface is less destructive, but repeated wetting and drying compounds the damage each time.
Smokeless Powder Reacts Differently
Modern smokeless powder is based on nitrocellulose, a very different chemical from the simple mixture in black powder. Water doesn’t dissolve nitrocellulose the way it dissolves potassium nitrate, so a brief exposure to moisture is far less catastrophic. Smokeless powder can even be stored wet intentionally as a safety measure during manufacturing and transport, since the moisture prevents accidental ignition.
That said, water does accelerate the chemical breakdown of nitrocellulose over time. Research on smokeless powders at varying moisture levels found that as water content increases, the energy required to trigger thermal decomposition drops. In other words, wet smokeless powder becomes chemically less stable, not more. The water speeds up a process called hydrolysis, gradually breaking down the nitrocellulose molecules. This is a long-term storage concern rather than an immediate hazard. Powder that gets briefly wet and is dried promptly will generally perform close to normal. Powder stored damp for months or years is a different story: it degrades unpredictably and should be discarded.
Risks When Firing Moisture-Damaged Ammunition
Using ammunition with moisture-compromised powder introduces two specific dangers that every shooter should recognize.
A squib load happens when the powder generates too little pressure to push the bullet out of the barrel. The bullet gets stuck partway down the bore. If you fire another round behind it, the barrel can rupture violently. Squib loads often produce a noticeably weak report and less recoil than normal. If something feels “off” about a shot, stop immediately.
A hangfire is a delayed ignition, where the firing pin strikes the primer but the round doesn’t go off right away. It might discharge a fraction of a second later, or up to several seconds later. Deteriorated or damp powder is one known contributor to hangfires, because the powder burns more slowly than designed. The danger is assuming the round is a complete dud, opening the action, and having it fire while the breech is open or the muzzle is pointed in an unsafe direction.
How Well Modern Cartridges Resist Water
Factory-loaded ammunition is surprisingly resilient. Modern cartridge cases create a fairly tight seal around the powder charge, and many military and premium loads add a ring of sealant around the primer pocket for extra protection. But even unsealed commercial ammunition performs better than most people expect when exposed to water.
In one controlled test, 200 rounds of both sealed and unsealed ammunition were submerged with their primers sitting in water. After 24 hours, the rounds were dried off and fired with no malfunctions and no meaningful drop in velocity. The remaining rounds stayed submerged for 30 full days, then were dried and fired. Again, no anomalies in either the sealed or unsealed ammunition. Muzzle velocities stayed consistent with dry control rounds across the board.
This suggests that brief accidental exposure, like dropping a box in a puddle or getting caught in rain, poses virtually no risk to modern factory ammunition. The brass case and primer cup do most of the waterproofing work on their own. Primer sealant adds an extra margin, but it isn’t strictly necessary for short-term water exposure. That said, the 30-day test represents the outer limit of available data. Ammunition stored in perpetually humid conditions for months or years, especially with visible corrosion on the case or primer, is a different situation and not worth the risk.
Can You Dry Wet Powder and Reuse It?
For black powder, the answer is effectively no. You can dry it, and it will ignite, but the performance will be poor and unpredictable. The dissolved and recrystallized nitrate changes the burn characteristics enough that you can’t trust it for consistent pressure or velocity. In a muzzleloader, this means erratic accuracy at best and a potential squib load at worst.
For smokeless powder, a quick accidental wetting followed by thorough air drying at room temperature leaves the powder in usable condition in most cases. Spread it in a thin layer in a well-ventilated area away from any heat source or ignition risk, and let it dry completely. Do not use an oven, heat lamp, or hair dryer. Smokeless powder that has been soaked for an extended period, or that shows clumping, discoloration, or an acidic smell after drying, should be disposed of. The chemical degradation from prolonged moisture exposure is invisible and makes the powder’s behavior unpredictable.
Storing Powder to Prevent Moisture Damage
Loose powder should be kept in its original factory container with the lid tightly sealed. Store it in a cool, dry location where temperatures stay relatively stable. Humidity is the slow killer: even powder that never gets “wet” absorbs ambient moisture over years in a damp basement or garage. A climate-controlled room or a storage area with a dehumidifier is ideal. Avoid airtight metal containers like ammo cans for powder storage, since any moisture trapped inside has no way to escape and will concentrate on the powder over time.
For loaded ammunition, the same principles apply. Keep it in a dry environment, ideally with desiccant packets if you’re storing it long-term. Inspect older ammunition for green or white corrosion around the primer, which signals moisture intrusion. Cartridges with visible primer corrosion may still fire, but the risk of a hangfire or squib load increases enough that replacing them is the smarter choice.