How thick does a gun case wall need to be?

Answer: Judge by dynamic load: at 32 kg with a 4x factor, 3.0 mm on 150 mm ribs is enough.

Why keep 35 mm of clearance in the cavity?

Answer: The smallest gap a gloved hand needs to grip an edge; with less, the rim coating wears first.

Does stacking really change wall thickness?

Answer: Yes. Three layers puts 64 kg on the bottom unit and four puts 96 kg, so thickness follows the worst case.

Why is the tolerance tighter than on a general-purpose case?

Answer: Because foam sits against that wall; a gap over 1 mm leaves the liner uncompressed.

What does the 4.2 mm corner buy?

Answer: Drop behaviour; the corner strikes first and the thickness keeps a crack out of the side wall.

Which number on the sheet matters most?

Answer: Clear cavity size; once it is wrong, no wall or rib tuning recovers the design.

Why Gun Case Wall Thickness Cannot Be Chosen by Feel

Quick answer: A gun case wall is derived, not drawn. Payload, the longest item the cavity must hold, and stacking layers set thickness, rib spacing and tolerance. Run the chain in that order and the numbers stop being a guess.

Where the Gun Case Specification Chain Starts
Cavity Size: Fit the Longest Item First
Wall Thickness and Structure: Corners, Ribs, Base
Load and Stacking: Turning Layers Into Thickness
Latches, Sealing and Tolerances: Onto the Drawing
FAQ

1. Where the Gun Case Specification Chain Starts

Early last year a unit replaced 30 units with three inputs: a 1010 mm longest item, a 32 kg ceiling, and three-layer stacking. There was no drawing to copy. Worked in order, the three gave a cavity of 1080 × 310 × 170 mm, a 3.0 mm flat wall, 4.2 mm corners and a shell under 14 kg. Later the cavity grew 60 mm and stacking went to four layers; base deflection moved from 0.7 mm to 1.3 mm and failed acceptance. Nothing in a gun case is independent, and one changed number moves the far end of the chain.

The order is fixed: load and cavity, then wall, then tolerance.

Input	Move	Result
1010 mm longest item	35 mm at each end	Cavity 1080 mm
32 kg load	Check at 4x, 128 kg	Wall 3.0 mm
Three layers	Bottom carries two	Corners 4.2 mm
170 mm depth	25 plus 20 mm liner	Height 235 mm

2. Cavity Size: Fit the Longest Item First

Length follows the longest item, width the widest section, depth the liner. Width is where drawings fail: dividers get left out and the third item is 15 mm short.

Gun Case: a graphite hard case in a grey plastic tray on an aluminium roller table, red indicator on the side lock, empty trays behind

Clearance is not optional: 35 mm at each end is the smallest gap a gloved hand needs, and below it long items go in at an angle.

Depth is liner arithmetic: 25 mm base, 20 mm lid, and the clear gap is the drawing number.

Oversizing costs twice: a cavity 20 mm too wide lets the item shift and loads the thinnest foam.

3. Wall Thickness and Structure: Corners, Ribs, Base

At 32 kg with a 4x factor the check is 128 kg, and 3.0 mm holds about a 1.6 margin. Five rules carry the rest:

Flat wall 3.0 mm, corners and latch seats 4.2 mm;
Three ribs, 6 mm high, 150 mm apart;
A ring rib on the base, 20 mm in from the edge;
Parting line off the seal channel, 4.5 mm deep;
Draft 1.2 degrees, none where foam sits.

Ribs shorten the span rather than add material: 220 mm down to 150 mm nearly doubles base capacity.

Corners are about drops: the corner lands first, and the extra thickness keeps a crack from reaching the side wall.

4. Load and Stacking: Turning Layers Into Thickness

Three layers puts 64 kg on the bottom unit for months, so acceptance reads residual deflection at 24 hours.

Gun Case: a navy hard case upright in a grey tray inside a white security lane, telescopic handle raised, roller conveyor and yellow-edged floor mats

The line is 1.0 mm at the base centre: load 24 hours, release, wait 30 minutes, read again.

Heat moves it: at 45 C the modulus drops about 30 percent and the same unit reads 1.3 mm, so hot stores stack lower.

Layer count also picks the wall: four layers means 96 kg, so 3.4 mm or ribs at 120 mm.

5. Latches, Sealing and Tolerances: Onto the Drawing

The latch decides whether the gasket compresses at all: 180 N plus or minus 15, with the seal at 28 percent inside a 24 to 32 band.

Item	Nominal	Tolerance	Measured by
Cavity length	1080 mm	±0.5 mm	Caliper, 3 points
Flat wall	3.0 mm	±0.2 mm	Ultrasonic, 5 points
Latch force	180 N	±15 N	Force gauge
Seal compression	28%	24 to 32%	Gap after closing

Tolerance is the first thing cut and the last that should be: half a millimetre on the cavity is what lets foam sit tight.

Conclusion

A gun case specification runs one way: payload and cavity go in, wall and structure come out, tolerance closes the loop. Any link filled in by feel is paid for later in trial moulds. Give every number a source, and the drawing survives acceptance.

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.