Somewhat related; We have visited a number of lighthouses around the Great Lakes and on more that one occation, have noticed some fairly large black powder cannons. These were used to project a rescue line to ships out on the lake. Basically they project a long weighted rod, with a line attached. As long as you have plenty of by-pass and no air pockets, there is not enough restriction to do any harm. The barrels I saw were about 4Ft. long and 8" OD. ..
Be Safe !!!