This is the airsoft version, I'll upload a reenactment version without the holes needed for the airsoft version.
I took inspiration from Wether Industrie's system to build French Defensive grenades.
Here's how to reload/assemble the fuse part :
The grenade and fuse assembly were printed in PLA+ and painted, the spoon and rivets are printed in silver silk pla.
I recommend using 3 or 4 walls at most to keep the weight down and not risk hurting your target.
I inserted a M3 cap head screw in the firing pin to improve reliability, the percussion cap nipple is a 4mm pop rivet reamed to 3mm to make room for the fuse. The spring is 9x20mm.
The safety pin was bent using a homemade jig from 1.5mm piano wire.