[Warning, this post contains cannon terminology] Why? Well, there is a reason TNT goes off to the side when shooting east or west, and it is not "wind". The answer: Triangles. Fixing the east / west patch is limiting triangle-tech In vanilla Minecraft, TNT always is moved first on the y axis, then the x axis, and finally the z axis. When a cannon is facing in the "x" direction (east / west), even if the TNT is slightly misaligned, it comes out of the cannon first and then goes to the side without hitting a backboard (to stop the perpendicular velocity). This makes it so the TNT has a slight perpendicular velocity. Of course, this is not the optimal, but the solution is very easy. Instead of having your propulsion in the center (where it is by default), align it after compression to the side of the cannon where everything else is so it does not exert a perpendicular velocity. But... what if I am using a left-shooter? ... Simply use triangles to your advantage! When firing east / west you must reach the target in one game-tick (before the triangle moves the TNT over), but it is still generally much easier to left / right shoot than with a traditional left-shot.