This is a prototype replacement shell for the Thunder B airsoft grenade, my first test print fits perfectly on my grenade, just make sure to print the filet with a low layer high like 0.1/0.5 for a better seal/fit.

You will need the best layer adhesion possible for obvious leakage prevention.
Also, play with the infill and the shells amount to change the propreties of the grenade but avoid printing only one shell, it will never explode.

When i tested the shell printed in PETG it exploded in a hundred sharp plastic pieces with enough force to probably penetrate skin, IT CAN WORK OR GO VERY BAD, THIS IS 3D PRINTING, YOU MAKE THE SHELL, YOU ARE THE MANUFACTURER AND YOU DO IT WITH EXTREME CARE AND EXPERTISE, DEPENDIND ON THE MATERIALS YOU USE IT CAN BECOME A VERY DANGEROUS THING. I do not recomend using this at an airsoft game, however, i'm leaving this online for community research purposes

NEVER APPROACH A GRENADE WHO DIDN'T EXPLODE, WAIT A WHILE TO LET THE GAS ESCAPE.

I AM NOT RESPONSIBLE FOR EVENTUAL INJURIES, BE SMART, BE SAFE. AND PLEASE, TEST YOUR PRINT BEFORE THROWING A DANGEROUS DICE ON THE FIELD.

Note: I will not improve the design, i can't test the grenades where i live. Also This was a proof of concept and should be threated like that.