The Ammo Can's War Story: From .50 Cal Boxes to Your Garage

Before the steel box

For the first decades of the machine-gun era, American ammunition traveled in wood. The Army's belted machine-gun rounds rode in wooden chests, and small-arms cartridges came in cardboard cartons packed into wooden crates.

Wood and cardboard have obvious problems in the field. They soak up rain, swell, rot and fall apart under rough handling. Ammunition that gets wet can corrode, and wet cardboard turns into pulp around the cartridges it was supposed to protect.

World War II forced the issue. American troops were fighting in North African desert, Pacific jungle and European winter, often at the end of long, wet supply lines. The Army needed a container that could survive all three.

This feature draws on Wikipedia's detailed entries on U.S. Army munitions packaging and ammunition boxes, plus reporting in GUNS Magazine. Dates are as those sources give them.

1942: the M1 and M2 boxes

In 1942 the Army introduced two steel boxes that would set the pattern for everything after.

• The M1 box held 250 belted rounds of .30-caliber machine-gun ammunition. Wikipedia's list of U.S. Army munitions says it opened from the side, had a flat bottom, a catch for the tripod, and oval ribs pressed into the sides for strength. It replaced the wooden M1917 machine-gun ammunition chests, which were less durable. It was made from 1942 to 1945 and phased out by the 1950s.
• The M2 box, from September 1942, was the bigger sibling for .50-caliber, holding 110 belted or 105 linked rounds. It had a foam-rubber gasket and opened from the front like a toolbox.

GUNS Magazine's Brent Wheat dates the "modern" ammo can to these same 1942 introductions, noting the larger 20mm "rocket box" arrived the same year.

The key innovation was not the steel. It was the seal. A hinged steel lid clamping down on a rubber gasket turned a box into a container that kept water out. Everything that came later is a refinement of that idea.

1945 to 1953: small improvements

The designs evolved quickly once soldiers started using them in volume.

• M1A1 (June 1945): slightly taller than the M1, with a more durable rubber gasket. It held 250 belted or 275 linked .30-06 rounds.
• M19 (1946 to 1953): a product-improved replacement for the M1 series. It kept the rubber gasket but dropped the tripod catch and had smooth sides. Its lid could lock partly open to protect a feeding belt from the weather.
• M2A1 (1950): the .50-caliber can most people picture today. It opened from the side, had smooth sides, a rubber gasket and a hollow bottom for stacking, and held 100 linked rounds.

Meanwhile, the Army also had a different solution for loose small-arms cartridges: sealed, single-use metal cans that had to be cut or keyed open. That is a separate story, and it is where the nickname "spam can" comes from.

Korea and the cold: the M19A1

The Korean War tested American equipment in brutal cold, and the ammo boxes did not escape. According to Wikipedia's munitions list, the M19A1, introduced in 1954 for the new 7.62mm NATO cartridge, specifically corrected Korean War problems:

• The lid and gasket were adjusted so the box would seal properly in cold weather.
• The latch was widened so it could be worked with gloved hands.
• The bottom was hollowed so boxes would stack securely.

Those three changes describe almost exactly what makes an M19A1 a good storage box today: a reliable seal, a latch you can open easily, and a shape that stacks. The M19A1 has remained in use from 1954 to the present. Wikipedia lists its military load as 220 linked or 225 belted 7.62mm NATO rounds.

GUNS Magazine adds that in the 1950s both the .30 and .50 boxes were redesigned with weatherproof seals, a new latch and lids that stack more easily, and that those redesigned boxes are the ones you are most likely to see today.

The M2A1 and its successor

The M2A1 served from 1950 to 2004. That year, according to Wikipedia's list, it was replaced by the M2A2, which added a reinforced hinge and a support bar to protect the gasket. Even the last update was about protecting the seal.

A military specification, MIL-B-3060, covers "Boxes, small arms ammunition: M19A1 and M2A1." That spec is the reason surplus cans from different makers and decades look nearly identical: they were all built to the same drawing.

From surplus to the garage

Once the military retired cans, they flowed into surplus stores, and from there into garages, boats, workshops and range bags. Wikipedia's ammunition box entry notes that used metal ammo boxes are widely repurposed for storage and are popular geocaching containers.

Two cautions from that same entry are worth repeating:

• Not for food. Used military boxes can carry lead and propellant residue inside, so they should not store food or drink. The old military cans themselves carried the warning "Do Not Use As Food Container."
• New or fully reconditioned boxes avoid the residue issue. Many retailers now sell newly made cans built to the military pattern.

Ammunition Depot, for example, lists a new M2A1 .50-cal can described as never used, steel, with a gasket seal, and interior dimensions of 11 by 5.5 by 7 inches. Its new M19A1 .30-cal can is listed as cold-rolled steel with a powder-coated finish, a gasket seal and an empty weight of 3.75 pounds.

Why the gasket is everything

Read the history again and one part keeps showing up: the gasket. The foam-rubber gasket of 1942, the "more durable" one of 1945, the cold-weather fix of 1954, the gasket support bar of 2004. The steel box is just a frame for the seal.

That matters for anyone storing ammunition by the case. Wikipedia's ammunition box entry puts it simply: metal boxes commonly have a rubber gasket in the hinged lid to protect ammunition from moisture. A can with a cracked, flattened or missing gasket is just a heavy tin box.

How to check a can's gasket

1. Look. Open the lid and inspect the gasket all the way around. It should be continuous, seated in its channel, and free of cracks, tears or flat spots.
2. Feel. It should be soft and springy, not hard or brittle. Old surplus gaskets often harden.
3. Close and press. A good can takes a little effort to latch, and you may feel air resist as the lid seals.
4. Check the lid and body. Dents near the rim or a bent lid can stop the gasket from seating even if the rubber itself is fine.

If a can fails, replace it or use it for non-critical storage. For long-term ammunition storage, a sound gasket, a silica-gel pack and a cool, dry room do most of the work. Our case storage guide covers the room, and our storage gear roundup covers steel versus polymer cans.

The can on your shelf

Next time you latch an M19A1, consider what is built into it: a 1942 idea about keeping water out, a 1954 fix for frozen Korean hillsides, and a latch made wide enough for a gloved hand. It is one of the few pieces of military equipment that civilians use for exactly what it was designed to do.

For bulk buyers, the practical lessons from eighty years of ammo cans are short:

• Buy cans with good gaskets, new if you can.
• Keep one load per can and label it.
• Store cans off the floor, in a cool, dry, locked space.
• Inspect gaskets when you rotate stock.

Browse new military-pattern and polymer cans in Ammunition Depot's ammo can category, or see ammo-in-a-can bundles if you want ammunition and storage in one purchase.

Editorial note: This is an independent editorial overview built from manufacturer specifications, retailer listings and published sources. We have not performed hands-on testing of the products discussed, and nothing here is a performance guarantee. Verify specifications, compatibility and the law where you live.

Affiliate disclosure: Some links on this page are affiliate links to Ammunition Depot. We may earn a commission if you buy through them, at no extra cost to you. Our editorial choices are not influenced by commissions. Check current price, stock and specifications directly with the retailer.