i made this tennis ball launcher for a friend, 20 inch 2.5 inch chamber, and 15 inch 2.5 barrel, i couldent find reducers, so i tapped the 1 inch nipple into the endcaps, the only reason i made it for him is if he tried to make one himself he would blow himself up....
it fires a tennis ball out of sight, but i tapped the 1 inch nipple on the barrel crooked.
