So I wanted to make dummy shells that use old hulls as the base, but without the hassle of running them through my reloading press and came up with this. I assume a fully printed shell would get chewed up by the extractor hence the marriage of the old hull to a printed slug

The print consists of two parts:

Part 1 is the cutting jig: Insert a spent shell and cut off excess plastic using a heavy box cutter. This should leave you with the brass and some plastic casing. Use the cut guide to draw a line, cut roughly, re-insert in cut guide, cut cleaner. Finally, file the end smooth and flat.

Part 2 is the slug: Print a half dozen of these. I added lead shot and some hot glue to the inside to give the slug weight (optional). Then hot glue the slug into your cut shell.

That's it. They come in approx 2 3/4 by design and the weight lets you practice loading and racking with decent realism.

I printed these fairly dense (90% infill, thicker walls) so they would last, but that's your call. Use supports when printing the cutting jig.

I tested these in my pump and they cycle beautifully.

DISCLAIMER - This is a training shell ONLY. There is no projectile, no powder and it is incapable of firing.