When two rows of TNT fight, which I did to try to make a powerful TNT cannon, It exploded one of the TNT blocks to the left, near the tip. As you may notice, the head piece of TNT was more to the left after activated. Normal TNT cannons DO NOT do this. I also tried without the head piece, and it still blew up, but at the left side each time. The head piece also moved to the left each time activated, however, it still blew up to the left without the head TNT piece.