How Long Does Ammo Last? Storage, Shelf Life and Buying Bulk at a Gun Show

Bulk ammunition is a fixture of show tables: sealed factory cases, loose rounds in zip bags, surplus in sealed cans and boxes from an estate that sat in a garage for years. Age alone rarely ruins a cartridge. Heat, water and chemicals do, and the box won’t say which of them it has met. Here is what the makers and the industry’s standards body say about shelf life and storage, and what to check before paying for old ammunition.

What the makers actually say about shelf life

Federal’s FAQ says to keep ammunition “in a cool, dry place, protected from direct exposure to sunlight,” and puts the shelf life of properly stored loaded ammunition and reloading components at 10 years. Remington’s FAQ gives the same figure, then adds the caveat that matters more: poor storage, “such as a humid or corrosive atmosphere, could cause product damage immediately.”

SAAMI, the Sporting Arms and Ammunition Manufacturers’ Institute, takes a longer view. Its information sheet on small arms ammunition says factory-packaged ammunition stored for extended periods, through ordinary temperature and humidity “ranging from tropic to Arctic conditions,” can be expected to work safely and well in the intended gun, if it is in proper working order. In Shooting Illustrated, George Harris explains the missing expiration date: properly stored, current ammunition is “projected to have an unlimited life span.”

The 10-year figure is the makers’ number, and Remington means it: its FAQ sends ammunition older than its shelf life, or exposed to fire, to local authorities for disposal. Storage counts for more than the calendar; one summer in a truck can do more harm than a decade in a hall closet. An NRA Family article quotes NRA Museums senior curator Doug Wicklund on firing factory loads from the 1870s, yet still advises shooting up carry ammunition after three to five years and buying fresh.

What ruins ammunition: heat, water and chemicals

SAAMI’s storage and handling recommendations name the culprits: extended high temperatures or humidity, and water, solvents, petroleum products, acids, ammonia and other chemicals. Its information sheet explains that such materials can reach the powder or primer and cause “misfires or squib shots.” A squib is the dangerous one. Winchester’s recall notice for certain 9mm loads describes how a bullet left stuck in the barrel puts the gun and shooter at risk if another round is fired.

Heat. SAAMI says to avoid temperatures over 150°F. Harris warns about sustained temperatures of 150 to 170 degrees, which he says car trunks, metal buildings and other uninsulated spaces in direct sun can reach. SAAMI also advises against leaving ammunition in a hot vehicle for long periods.

Chemicals. Harris writes that penetrating oils and cleaning solvents slowly break down the sealants and can kill the primer, the powder or both, and that ammoniated bore solvents can crack unfired brass. Ammunition stored beside the cleaning kit has had exactly the wrong kind of care.

Old primers. American Rifleman explains that early mercuric primers tended to decompose in long storage, causing misfires and hang-fires, and that potassium chlorate priming leaves a water-attracting salt that speeds corrosion. Non-corrosive primers reached sporting ammunition in the 1920s, but the military kept corrosive priming through World War II and beyond.

Reading an old box at the table

SAAMI’s handling rule is the standard: check each round before use and throw out any that is corroded, deeply dented or deeply scratched. Then the sentence worth memorizing: “If in doubt, do not chamber or fire the ammunition.” Here is what doubt looks like.

Mixed headstamps in a box that should hold one maker’s rounds suggest it was repacked.

Fire, flood and the salvage-box problem

SAAMI’s information sheet is blunt: ammunition wetted or scorched in a structural fire, or exposed to floodwater, should never go back into commercial sales or be sold at salvage sales, because the exposure could make it dangerous to the shooter. “It should be scrapped.” A seller may not know, or may not mention, that a box came out of a flooded basement, so ask.

Two SAAMI advisories revised in February 2025 go further. On heat, SAAMI says ammunition that may have been exposed to temperatures above about 200°F should be disposed of, and adds: “The fact a round did not initiate during a fire should not be taken as a sign that the product is not deteriorated.” On water, it says “the safe answer is to NOT attempt to salvage or otherwise use previously submerged ammunition.” Don’t ship it back to the maker; ask local law enforcement about disposal.

If your own house burns, the news for firefighters is better than the movies suggest. SAAMI’s firefighter video, made with the International Fire Chiefs Association after tests using more than 400,000 rounds, shows that sporting ammunition outside a firearm is unlikely to ignite from impact, does not chain-react, does not mass explode and can be handled with water and standard structural gear with breathing apparatus. A loaded gun is the exception: SAAMI warns that a chambered round set off by fire sends the bullet down the barrel as if the trigger were pulled, while loose cartridges will likely just burst. That is one more reason to store ammunition apart from firearms.

Factory boxes, repacks, surplus and reloads

The biggest difference between bulk offerings is how much paper trail survives. In Shooting Illustrated, Richard Mann explains that every box gets a lot number, often stamped inside the flap of a cardboard box, which makers use to pull records, including pressure-test data, when a problem is reported. Recalls work the same way: Hornady’s 2024 recall of certain 350 Legend lots told owners the lot number is printed on the box label. A bag of loose rounds has none. SAAMI adds that original labeling helps keep ammunition matched to the gun it was made for. Don’t expect a manufacture date; if age matters, give the maker the lot number and ask.

With surplus, assume corrosive primers unless the labeling says otherwise. Shooting Sports USA’s Art Merrill notes that corrosive residue is manageable with water-soaked patches; our milsurp rifle ammo guide covers which rifle fires what and the cleanup. Steel cases are a poor bet for reloading; Harris says it can be done but calls it “more trouble than it’s worth.”

Reloads are the easy call. Nobody can see a powder charge through a case. Federal law also bars being in the business of manufacturing ammunition without a license (18 U.S.C. 923(a)), so a table selling its own loads should be able to say who loaded them and under what license. If the answer is a shrug, keep walking. Our used reloading gear guide explains why other people’s components deserve the same caution.

How to store what you bring home

• Cool and dry. SAAMI calls for a cool, dry spot away from solvents, chemicals, heat sources and flames. Wicklund’s ideal, per NRA Family: “Around 70 degrees with 50% humidity.”
• Original packaging. SAAMI recommends the original packaging or other packaging made for ammunition. The box keeps the lot number with the rounds.
• Sealed cans and desiccant. NRA Family suggests an airtight or O-ring-sealed container with an anti-humidity pack inside. Harris says sealed military-surplus cans in a climate-controlled, secure spot “will preserve the ammunition indefinitely.” Put factory boxes inside the can.
• Off damp floors. SAAMI suggests stacking cartons on pallets where a basement floor gets damp.
• Away from oils and solvents. NRA Family warns both can eventually work into the cartridge.
• Locked and out of children’s reach. SAAMI calls for a locked closet or cabinet out of children’s reach, with ammunition kept apart from firearms and away from unauthorized people. Remington says the same.
• Rotate. Shoot the oldest first.

Shopping for locked storage at the same show? Our gun safe guide explains show specials and what fire-rating labels do and don’t promise.

The legal side of buying ammunition at a show

Federal law sets the floor for licensed sellers: no ammunition to anyone they have reason to believe is under 18, and only rifle or shotgun ammunition to anyone under 21 (18 U.S.C. 922(b)(1)). A dated caveat: on September 18, 2026, the Justice Department said the under-21 limit cannot be criminally enforced against dealers selling handguns to law-abiding 18- to 20-year-olds. That covers handguns, not ammunition, and the statute is unchanged. States add more.

The California Department of Justice says ammunition sales generally must go through a licensed California ammunition vendor, each buyer must first pass an eligibility check, and residents may not bring home ammunition bought out of state unless it is first delivered to a licensed vendor, with limited exemptions. The check is under challenge in Rhode v. Bonta; the Ninth Circuit heard it en banc on March 25, 2026, and had posted no decision as of September 29, 2026. New York requires a dealer or ammunition seller to run a background check before selling to anyone who isn’t also a dealer or seller.

Buying new instead: what to look for online or at a dealer

For ammunition you plan to keep for years, new production with a known lot is often the better value once risk is priced in. Compare these points.

• Price per round, delivered. The U.S. Postal Inspection Service says small arms ammunition can’t go through the mail, and UPS carries it by ground within the contiguous 48 states (plus intra-Oahu and intra-Alaska) only when marked as a Limited Quantity; anything else needs a contract. Divide the total, shipping and fees included, by the round count. Our show versus online pricing comparison covers the rest.
• Lot consistency. Lots can shoot differently, and Mann’s advice for precision work is to buy plenty of the lot you like. Ask whether a multi-box order ships from one lot.
• Primer type. Look for non-corrosive priming, and for brass, Boxer-primed cases if you may reload.
• Packaging. Factory boxes with a printed lot number keep recall and defect questions simple.
• Shipping restrictions. Confirm the seller ships to your state and address. A California resident’s out-of-state order must go to a licensed vendor.
• Return policy. Expect final-sale terms at many sellers, including some manufacturers’ own stores. Ask how a defective box is handled, and keep the lot number.

Local gun shops, sporting goods chains, online ammunition retailers and some manufacturers’ web stores carry common calibers; odd ones may need a special order.

A table-side checklist for old ammunition

1. Ask where it was stored: house, basement, garage, shed or vehicle.
2. Ask whether it was ever wet or near a fire. Pass on any yes.
3. Look for a factory box with a readable lot number and headstamps that match it.
4. Open more than the top box.
5. Check cases under a light for crust, rust, pitting, cracks and deep dents.
6. Compare bullet seating across a handful of rounds.
7. Look for water stains, warping, soot or a smoke smell on the cardboard.
8. For surplus, assume corrosive priming and price in the cleanup.
9. Pass on reloads of unknown origin, however tidy the labels.
10. Confirm your state’s purchase rules before money changes hands.

Add a small flashlight to your show-day checklist, then pick a date from the gun show calendar. The best bulk buy is the one whose history you can actually learn.