Shotgun Safety Flag, Improved

This is V3.0 of a parametric design for a shotgun safety flag in sizes from 12 gauge to .410, aimed (ahah) primarily at users of pump action and semi-automatic shotguns but useful for break actions and large calibre rifles.

Its main advantage over other designs is that the lug that goes down the barrel is split down the middle into two prongs. Should a bit of a prong break off, the two parts interlock sufficiently for the broken part to be pulled out with the intact part. If it doesn't come out with the rest of the safety flag, the thin fragment will not cause a bore obstruction and will most likely fall straight through the barrel. If both parts break off, they do not interlock sufficiently to hold them in the barrel.

Printing

This is designed to print without support and brim. It prints well in PLA but due to heat and physical stress, 4 perimeters and 30%+ infill are recommended. You should just be able to print, lift, and give to shooting club members.

Improvements

The V2.0 worked well, but testing on the range revealed users who were just handed one were inclined to put one prong of the flag in the chamber and drop the bolt on it to keep it in. This invariably broke it, but proved that the bits did indeed fall out as designed.

To solve this, the V3.0 flag has been made thicker and stronger, and interlocking teeth have been added at the front to prevent people inadvertently slipping it over the side of the receiver. The fit is now tighter (hopefully people will no longer feel the need to drop the bolt on it), and it is not possible to over-compress the mechanism and break the prongs off inwards.

Due to popular demand the corners were bevelled to stop it poking holes in your pocket. This also made it easier to print without a brim.

Notes

In the OpenSCAD source, the embossing on the flag can be changed to indicate the intended calibre. A logo may be added on the underside.

A .410 safety flag will also conveniently fit the chamber of a .45-70 rifle.

The main change is to stop it being inserted incorrectly and broken. It has been made a better fit, stronger, and thicker. Numerous changes have been made to the OpenSCAD source to improve the parametric performance.