Why is an ammunition container usually rotomoulded rather than injection moulded?

Answer: Bodies run 600 to 1,200 mm, needing a machine above 1,000 tonnes and a tool from 150,000 yuan. An ammunition container rotomould costs 30,000 to 80,000 yuan and starts at 300 units.

What separates a 3 mm wall from a 6 mm one?

Answer: Three suits injection moulding, uniform but rib-dependent. Six tops the rotomoulding range, stiff but slow to cool. Four to five is the balance.

Do ribs leave sink marks on the outer face?

Answer: Once rib width passes 70 percent of wall thickness. Hold it at 60 percent with a 3 mm fillet and the mark disappears.

What is the seal cord made of?

Answer: EPDM at 60 Shore A, compressed about 25 percent, resisting ozone and ultraviolet.

Will the hardware rust?

Answer: Not the stainless pin, but a plated bracket touching it will. A plastic bush plus 8 µm of zinc keeps red rust away through 48 hours of salt spray.

Ammunition Container Structure and Process: Five Points

Quick answer: An ammunition container is five parts in one shell: upper and lower halves, the lid rebate, the seal groove, the ribs and the hardware. Bodies above 800 mm are usually rotomoulded, and thickness runs 3 to 6 mm with ribs carrying the load.

What an Ammunition Container Body Is Made Of
Rotomoulding or Injection Moulding
How Thickness Is Distributed from 3 to 6 mm
Ribs, Stacking Faces and Corner Geometry
Hinges, Latches and Hardware Corrosion
FAQ

1. What an Ammunition Container Body Is Made Of

An ammunition container looks like a single moulded shell, yet five elements work together: upper and lower halves, the lid rebate, the seal groove inside it, inner ribs, and hardware through moulded holes.

On an 800 mm body each half weighs about 3 kg and the rebate runs 8 to 12 mm deep. Too shallow and the lid shifts; too deep and it drags. The 6 mm groove leaves roughly 25 percent compression once the cord is in place.

2. Rotomoulding or Injection Moulding

Size, batch and complexity decide the process. Rotomoulding suits hollow shells above 300 mm, double walls and moulded-in inserts; injection moulding suits small, tight parts above 3,000 units.

The crossover sits near 2,000. A rotomould costs 30,000 to 80,000 yuan against 150,000 to 400,000 for an injection tool on a 650 to 1,300 tonne machine. Injection cycles run 40 to 70 seconds, rotomoulding 18 to 25 minutes.

Item	Rotomoulding	Injection moulding
Tooling	30,000–80,000 yuan	150,000–400,000 yuan
Cycle	18–25 minutes	40–70 seconds
Wall tolerance	±0.8 mm	±0.5 mm
Economic batch	300+	3,000+

Material splits the same way: LLDPE powder at 35 mesh for rotomoulding, nylon with 30 percent glass fibre for latches that stay tough at minus 20 °C.

3. How Thickness Is Distributed from 3 to 6 mm

In rotomoulding the wall forms as powder fuses against the hot mould, and gravity thickens the base. A body specified at 5 mm often measures 5.5 mm at the base and 4.5 mm at the side.

Injection moulding takes thickness from the cavity, so variation stays under half a millimetre, which lets such a part run at 3 mm while a rotomoulded one starts at 4 mm.

Thicker is not stronger. Past 8 mm, rotomoulded walls trap bubbles where powder fails to fuse. Judge thickness at the rib roots and base transition, keeping the thinnest reading above 3.5 mm. The lid rim runs half a millimetre thicker than the side wall, because the rebate is squeezed at every closure.

4. Ribs, Stacking Faces and Corner Geometry

Rib geometry follows three numbers: 8 to 12 mm tall, 60 percent of wall thickness wide, and a root fillet of at least 3 mm. Past 70 percent width, sink marks appear outside; without the fillet, the rib root cracks first.

Layout sets the load path. A rib grid spreads force to four edges and suits the base; single-direction ribs resist bending in one axis and belong on side walls. Stack five high and the bottom case carries four above it.

Stacking depends on contact area. Keep the top face flat within 1 mm, radius corners at 15 mm or more, and mould a 2 mm recess so the base above drops in. A domed top leaves a line of contact instead.

5. Hinges, Latches and Hardware Corrosion

Hinges are either a living hinge moulded with the shell, a stainless pin through moulded ears, or a separate metal hinge. An ammunition container body mostly uses the pin, since a living hinge tears on a thin wall.

Latches should hold at least 300 N and be moulded in glass-filled nylon, with load on a thickened boss.

Hardware	Material	Finish	Salt spray
Hinge pin	304 stainless, 4 mm	Passivated	96 hours
Padlock lug	Plated steel	8 µm zinc	48 hours

Corrosion risk sits at dissimilar contacts. A stainless pin in a plated bracket needs a plastic bush, or galvanic corrosion starts in damp air and the plated part fails first.

Conclusion

An ammunition container is five elements in one shell: body, rebate, seal groove, ribs and hardware. Process splits on size and batch, thickness from 3 to 6 mm is carried by ribs and fillets, and hardware survives on material pairing. Structure sets the service life of an ammunition container; process only delivers it.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.