I wanted to shoot silly shells from my SledgeFire. I had to do a lot of shell cutting, but it worked, kinda. Maybe with more springpower, but it shoots Mega and 3 shot shells well. You can throw a MegaXL farther by hand, though.

I made a cover for the air seal that smushes a piece of Silicone cooking sheet (1/16 inches thick) to the back of the shell to make a seal. It is only one mm thick, but seems to do the trick. Of course, I removed the air restrictors and sanded the original face smooth to glue it.

I also included the “breech” that holds the shell in the barrel and keeps the seal, however I found it also makes a good sanding tool when you're trying to sand the inside of the SledgeFire to fit the barrel into it.

Also included my Bambu Lab A1 3MF file with the settings i used to print.

Test Fire: