Does a gun case need salt spray testing on arrival?

Answer: At 24 hours, yes. It shows whether hinges and screws bloom with rust in the first week, a handling question, not a coating one.

Can a gun case cavity be worked out from the outside?

Answer: No. Ribs and draft take 2 to 3 mm at the corners, where fit matters. Ask for cavity size on the drawing.

The supplier sent a third-party report. Do we still inspect?

Answer: Yes. It covers what was sent, not what arrived. Three checks take half a day: cavity, weight, pressure.

What happens when a lot fails on one MA unit?

Answer: The acceptance number decides: at AQL 1.0 with 50 samples, one defective passes, two fail.

Gun Case Inspection: 5 Checks, 3 Defect Classes, 50 of 500

Quick answer: A gun case passes on five measurable checks and fails on three defect classes. At 500 units, level II sampling means 50 cases, and the acceptance number sits in the contract, not in the inspector's judgement.

Five Checks a Gun Case Must Pass
Where the Five Thickness Points Go
Hardware, Torque and Feel
Why 500 Units Get 50 Samples
Salt Spray and the Test Calendar
Reject, Concession or Rework
FAQ

1. Five Checks a Gun Case Must Pass

Arrival inspections usually end with a photo of an open case. The photo proves delivery, not that two hundred gun cases still close after a season on the road.

The order is fixed: outline, cavity, wall, hardware, seal. Outline comes first because everything else is measured against it. Let the length run 1.5 mm over and later readings stop being numbers.

Check	Method	Pass line	Sampling
Outline, corners	Tape, calipers	±1.5 mm, no short shots	Every unit
Cavity	Calipers, five points	1150 mm up, ±0.8 mm	Every unit
Wall, weight	Ultrasonic gauge, scale	3.2 mm ±0.25, 4.6 kg	10 per lot
Hardware	Torque wrench, force gauge	Screws 1.1 N·m, latch 45 to 70 N	5 per lot
Seal	Gauge, water tank	0.35 bar, 45 s, 0.015 bar max	3 per lot

CR is a through crack, a popping latch, a seal that will not hold. One such unit fails the lot. MA is wall under tolerance, a chipped corner, a hinge screw below torque. MI is colour drift, flow marks, a light scuff inside. The MA and MI line needs a boundary sample, sealed and signed.

2. Where the Five Thickness Points Go

Readings come from the four corners and the base centre; the smallest counts.

Gun Case: overhead view of an open graphite shell, twin sealing ridges along the rim, foam base with a square recess holding a bevelled panel

Corners of a gun case run 0.1 to 0.2 mm thinner than the centre, so an average hides the spot that takes impact. Skip pin marks and rib roots, which read thick. Weighing is quicker: 0.05 mm off a 4.6 kg wall reads 100 g light.

3. Hardware, Torque and Feel

Hardware gets skipped because it needs tools.

Latch force on a gauge: 45 to 70 N. Under 45 N it opens in transit.
Hinge screws at 1.1 N·m on five units; one loose sends the lot back.
A 0.04 mm feeler gauge round the rim; 30 mm of slide means the face is uneven.
Valve pressed ten times, no rattle, no reverse leak.
One unit through 5000 cycles, latch wear under 0.3 mm.

4. Why 500 Units Get 50 Samples

ISO 2859-1 level II puts 281 to 500 units at code H, a sample of 50.

Gun Case: navy shell lying on a steel bench, black latch and rivets at right, folding handle beside a round pressure valve, scuffed corners

Lot	Code	Sample	MA 1.0	MI 2.5
151–280	G	32	0 and 1	1 and 2
281–500	H	50	1 and 2	3 and 4
501–1200	J	80	2 and 3	5 and 6
1201–3200	K	125	3 and 4	7 and 8

CR is never sampled. MA at AQL 1.0 fails on the second defective; MI at 2.5 allows three. Permit a second sample and the AQL moves down a step.

5. Salt Spray and the Test Calendar

Salt spray runs 24 hours per lot, 96 hours for the type test. Cold and heat take four hours each, from -20 °C to 55 °C. Damp heat runs 48 hours at 40 °C and 93 percent RH, then the lid comes up to check for condensation. Pressure stays on every lot: 0.35 bar, 45 seconds, 0.015 bar at most.

New resin, new mould or new hardware supplier resets the type test, since the change surfaces only in the next shipment.

6. Reject, Concession or Rework

Three routes, written down before the first delivery.

Return: any CR unit, at the supplier's freight cost, resampled from zero.
Concession: MA counts between Ac and Re, accepted with 3 to 8 percent off.
Rework: MI units sorted on site, resampled at 80.

An 8D within seven working days; two lots with the same MA finding suspend supply.

Conclusion

Five checks, three classes and one sampling table turn an argument into a decision. The numbers hold only if they sit in the contract beside a sealed boundary sample and a deadline for the 8D. Acceptance then stops depending on who is on shift, the only honest test of a gun case inspection.

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.