I made the barrel about 5 inches long which seems to increase the power quite a bit. I got some air soft BB's to go through about 6 layers of cardboard and 2 coke cans in a row. I also made the back screw on and off for easy clearing of the barrel between firing. Just need to drill the hole in the cap to the size of the fuse. Shot a box of black cats threw it and the cap and threads survived. I redesigned the cap 4 times before I got one to work.