Chamber Flags with Dummy Round Pegs, 32 Calibers

What it is

Each flag pairs a full-length dummy round, modeled on the real cartridge outline, with a bright hex tag that sits outside the ejection port. Drop one in and everyone on the line can see at a glance that the chamber is empty and the action is open.

Quick start

1. Find your caliber below.

2. Download the file that starts with its group, for example, Pistol - 9mm Luger.stl.

3. Print flat in hi-vis PETG with no supports.

4. Dry fit it with the action locked open.

Calibers

• Rimfire: .22 LR, .22 WMR, .17 HMR

• Pistol: .380 ACP, 9mm Luger, .40 S&W, 10mm Auto, .45 ACP, 5.7x28mm

• Revolver: .38 Special, .357 Magnum, .44 Magnum

• AR-15: 5.56 / .223, .300 Blackout, 6.5 Grendel, .350 Legend

• AK: 5.56 NATO, 7.62x39, 5.45x39

• Rifle (AR-10 and bolt action): .308 / 7.62x51, 6.5 Creedmoor, .243 Win, .270 Win, .30-06 Springfield, 7mm Rem Mag, .300 Win Mag, 7.62x54R

• Lever: .30-30 Win, .45-70 Govt

• Shotgun: 12 Gauge, 20 Gauge, .410 Bore

Print settings

• Material: PETG (ABS or ASA also fine)

• Color: hi-vis orange, yellow or green. Never brass, copper, silver or gray.

• Supports: none, print flat as exported

• Layer height: 0.2 mm

• Walls: 4

• Top and bottom: 5 layers

• Infill: 40% gyroid

• Brim: optional, helps long rifle pegs stick

• Filament: 8 to 44 g per flag

Two-color (AMS or MMU)

1. Import the AMS body and AMS accent files together.

2. Choose to load them as one object with multiple parts.

3. Set the accent to black and the body to your hi-vis color.

4. Slice and print. The back logo color change starts on layer 1.

How it fits

• Sizing: every diameter is 0.5 mm under SAAMI/CIP maximum cartridge dimensions, so the round drops in and slides out by hand.

• Rod: clears the barrel extension, trunnion or cylinder face. Revolver 6 mm, rimfire and pistol 8 mm, lever 12 mm, shotgun 18 mm, AR-15 22 mm, rifle 24 mm, AK 26 mm.

• Arm: holds the bolt off the round. On actions that don’t lock open, the carrier rests against it.

• Underside: flattened for printing. The small fin under the bullet stays inside the bullet’s diameter, so nothing reaches the rifling.

Safety

• A chamber flag is an indicator. Always check the chamber visually and physically yourself.

• Dry fit each flag with the action locked open. It should seat and come out by hand without force.

• Don’t insert a flag into a hot chamber right after firing. PETG softens around 80 °C.

• Check your range and match rules. Some don’t allow flags shaped like ammunition.

• Keep printed flags separate from live ammunition.