What actually changes in the cold
A cartridge is a small chemical system. The propellant inside is designed to burn at a controlled rate, and that rate depends partly on temperature. Ammunition maker Norma puts it simply: propellant burns faster in heat and slower in cold.
Slower burning means a little less pressure behind the bullet, which usually means a little less velocity at the muzzle. How much depends on the specific propellant and load. Some modern propellants are marketed as temperature-stable, meaning the maker designed them to vary less across a wide temperature range.
For most hunters, the practical effect is small at normal distances and grows with range. A deer at 100 yards will rarely notice. A shot at several hundred yards might.
Point of impact and your zero
Lower velocity means the bullet drops a bit more over distance. If you zeroed your rifle on a warm September afternoon and you're hunting in late-November cold, your bullets may strike slightly lower at longer ranges than they did at the bench.
Cold also affects other things that move your point of impact:
- Denser air. Cold air is denser than warm air, which adds a little drag.
- Your clothing. A thick coat changes how the rifle fits your shoulder and how you hold it. That can shift impacts more than the ammo does.
- Stock and bedding. Some rifles shift slightly as materials contract in cold.
The fix is simple: confirm your zero in conditions close to the ones you'll hunt in, wearing the clothes you'll hunt in. If you shoot long range, record your dope at different temperatures, or use a ballistic calculator that takes temperature into account. Our deer hunting ammo guide covers choosing a load in the first place.
The gun matters more than the cartridge
Most winter malfunctions aren't ammunition failures. They're gun problems that look like ammo problems.
- Thick lubricant. Oil and grease that work fine in warm weather can stiffen in deep cold, slowing a firing pin or a semi-auto action. Many shooters clean off heavy grease before winter and use a light lubricant rated for low temperatures. Follow your gun maker's guidance.
- Ice and snow. Snow in the barrel or action is dangerous. Check the muzzle after a fall or after setting the rifle down in snow, and never fire with an obstructed bore.
- Light primer strikes. A sluggish firing pin from thick lube or ice can cause a misfire that looks like a "bad round."
- Semi-auto cycling. Slightly lower energy plus stiff lubricant can cause short-stroking in some guns, especially with light loads. Test before relying on it.
If you get a misfire, follow safe handling: keep the muzzle pointed safely, wait several seconds in case of a hangfire, then clear the round as your manual describes.
Condensation: the real winter enemy
Moisture is the main thing that degrades ammunition in storage, and winter creates it in a sneaky way. Bring a cold rifle and cold ammo into a warm, humid house, and water condenses on every surface, including the inside of the action and the outside of your cartridges.
A few habits help:
- Let gear warm up in a case. Leave the rifle in a closed case for a while after you come inside, so it warms slowly and condensation forms on the case, not the gun.
- Dry and wipe down. Once it's at room temperature, wipe off moisture and check the bore.
- Keep hunting ammo dry. Carry it in a pocket or pouch, not loose in a wet coat. Wipe off any rounds that got wet before storing them.
- Use sealed storage at home. A gasketed ammo can with a desiccant pack limits humid air. Ammunition Depot carries metal and plastic ammo cans in common sizes.
Our guide to ammo storage, humidity and heat explains why stable, dry storage matters more than any single temperature number.
Is it safe to store ammo in a cold garage?
Cold by itself isn't usually the problem. Temperature swings and moisture are. A garage that goes from freezing at night to warm in the afternoon sun can cycle humid air into containers and create condensation over and over.
If you must store ammunition in a garage or shed, use sealed containers with fresh desiccant, keep them off concrete floors, and check them periodically. A climate-controlled closet inside the house is usually a better choice. Our ammo shelf life guide covers long-term storage.
Handguns and carry ammo in winter
Winter changes concealed carry too. Heavy coats add layers between your pistol and the outside world, and some defensive hollow points are designed specifically to expand reliably through heavy clothing. Check the maker's stated testing if that matters to you.
The bigger point is practice. Draw and shoot (where your range allows it) while wearing your winter layers. A coat that snags your draw is a bigger problem than a few feet per second of velocity.
A winter checklist
- Confirm your rifle's zero in cold conditions, wearing hunting clothes.
- Switch to a light, cold-rated lubricant and remove heavy grease.
- Check the muzzle and action for snow and ice before every shot opportunity.
- Carry ammo in a dry pocket or pouch.
- Let gear warm up in a case before opening it indoors.
- Store ammo in sealed containers with desiccant, away from temperature swings.
- Function-test semi-autos with your actual load in the cold.
Shotguns and rimfires in the cold
Shotgun hunters and rimfire shooters face a few cold-weather quirks of their own.
- Semi-auto shotguns: light target loads that cycle fine in summer may short-cycle in cold weather, especially with thick lubricant. Many duck and goose hunters use the heavier field loads their gun's manual recommends, and keep the action lightly lubricated.
- Plastic hulls: shotshell hulls are fine in the cold, but wet shells should be dried before storage.
- Rimfires: performance in the cold can vary from one .22 LR load to another. If you hunt small game in winter, try your load in cold conditions before relying on it.
Whatever you shoot, the principle is the same: test your actual gun and load in conditions close to the ones you'll face.
Frequently asked questions
Does cold weather make ammo less powerful?
Slightly. Propellant burns more slowly in the cold, so velocity usually drops a little. The amount depends on the load and propellant.
Should I re-zero my rifle for winter?
Confirming your zero in cold conditions is a good idea, especially for longer shots. Wear the clothing you'll hunt in, since fit changes can move impacts too.
Can ammo freeze?
Cartridges don't freeze in a way that ruins them. The bigger risks are moisture and condensation, plus guns that function poorly from ice or thick lubricant.
Is it bad to store ammo in a cold car?
Storing ammo in a vehicle long term isn't recommended, mainly because of temperature swings, moisture and security. Bring it inside and store it in a sealed container.
Why did my gun misfire in the cold?
Often it's the gun, not the round: thick lubricant or ice can slow the firing pin. Follow safe misfire procedures, then clean and use a cold-rated lubricant.
Editorial note: This guide is based on manufacturer information, published references and retailer listings. We haven't tested ammunition or firearms hands-on in cold conditions. Effects vary by load, propellant and firearm, and your gun's manual is the authority on lubrication and handling. We may earn a commission from links on this page at no extra cost to you.
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