I needed some snap caps for dry fire practice, as well as to get my kid to understand the working of firearms only to realize that the ones in market are decently expensive. I realized that I always have a lot of spent casings every time I go to the range so I designed an insert that can be pushed inside a spent case and to create a snap cap. 

The benefit is that printing 25 of these takes a couple of hours and I now have enough that I can run them every time I need to test and gift others so that the chances of negligent discharge comes down substantially. 

Two models, One individual insert and a group of 25. Built a grouped model as on smooth plates, I needed a raft and 25 individual inserts created overlapping rafts so a combined model worked better with a single raft. Here are the print details:

• Filament, PLA, PETG, PLA+. 
• Layer Thickness - .2mm or .3mm (higher thickness makes the surface too rough to load correctly)
• Infill - 15% gyroid is enough

Note: There is always a slight difference in size of PLA vs PET. This is slightly tight in PLA so need a bit of a force to go in and stays snug. With PET, you may want to insert a couple of drops of glue or rubber cement at bottom.