My previous tests with 3D printing 40mm projectiles failed. Printing them with my usual 15% infill had these projectiles weak enough that the force of the propellent charge would blow a hole right though the projectile.
I saw online someone else was having the same issue with the projectiles, but they reported they were able to 3D print 40mm shell cases and get two uses out of them.
This peaked my interest, and I revisited the problem.
I printed a couple different pusher designs, and a solid projectile. I also printed a case based off the standard 40mm training casing.
I loaded the solid 3D printed projectile into a case, and I had a cracked blue nose-cap, so I glued that to one of the printed pushers. The resulting projectile was extremely light, and I was unsure if it would fly correctly.
The printed projectile impacted low and bounced over the berm, so I didn’t get to recover and inspect it. I would hope it would be reusable, but even if it wasn’t, it would still be cheaper than the training rounds.
I’m not sure what happened to the other projectile (the pusher with glued on cracked cone). With it being light weight, I’m not sure if it flew off where I didn’t see it, or broke apart in flight. In the video, it sounds like it impacted the berm.
I had cracked the mouth of the case prior to firing it when I was trying loading various projectiles into it.
While this might look like a failure, I would call it a specular success. First, it worked. Secondly, there are no reinforcements in this printed test part. The printed 40mm case design could be reinforced, heavily. And third, a printed case could be made to use more commonly available 9mm or 45 auto brass. That way even if the brass failed with each shot, it would still be cheaper to reload.
I’m going to have to play around with this a bit more.