East Africa had a problem awhile back with semi-nomadic tribesmen stealing the 1/2” water pipe used as pump rods in the hand pumps scattered throughout remote regions.
These warriors proceeded to turn these pieces of 1/2” water pipe into gun barrels.
Street gangs in Papua New Guinea make guns to go with their machetes.
http://www.freerepublic.com/focus/f-chat/3012964/posts
We were in Des Moines last weekend at the State Historical society. They had on display a primitive cannon where the barrel is made of wood and then it was wrapped the entire length in wire to give it’s strength.