I recomend printing this model vertical with the projectile upwards. You need to use brim and supports, otherwise the top will sway as its such a narrow construction and the vibrations will cause a bad print.I included a model of the projectile so that you can calculate how much you need to enlarge or shrink the model to fit your cannon barrel. The projectile is the same diameter as the cylinder that goes into the cannon barrel so just messur your barrel diameter and pull the projectile through your slizer. Shrink or enlarge until you get the messurement you need. Then you can just use the same percentage of shrinking or enlagring o rezize the rest of the models.