Miss Fortune ult, When she shoots with her ult, are they Cannonballs or Bullets that she is shooting. Since she is a pirate hunting pirate she uses cannonballs and has cannonballs with her other abilities. But my friend says they are bullets bc her ult is called Bullet Time. But in the abilities art work they are Sphere balls which point to CANNONBALLS.
Muskets and pistols from the older eras used round lead balls as bullets. They look like tiny cannonballs, so her shots are actually that style of bullet.
In actuality, this style of bullet was much more damaging to people and structures than modern bullets. Because they were lead balls, not only would they cause lead poisoning in their targets, they would also soften when the gun combusted to fire them, and when they hit something hard, like bone, they'd "splatter" and flatten out causing much more internal damage to someone who got shot. They also were much less likely to pass through a target like modern, pointed bullets, which again made them that much more lethal.
Miss Fortune ult, When she shoots with her ult, are they Cannonballs or Bullets that she is shooting. Since she is a pirate hunting pirate she uses cannonballs and has cannonballs with her other abilities. But my friend says they are bullets bc her ult is called Bullet Time. But in the abilities art work they are Sphere balls which point to CANNONBALLS.
Bullets were spherical and being spheres is not what makes something a cannonball. The word bullet even means "little ball". Your friend is correct (but not for that reason).
The ult shoots waves of bullets. First of all, the ult is literally called "Bullet Time!" The game itself makes the conjecture that they are bullets, not cannonballs. Also here are the primary definitions from dictionary.com that actually relate to the topic.
Bullet Noun 1. a small metal projectile, part of a cartridge, for firing from arms Cannonball Noun 1. a missile, usually round and made of iron or steel, designed to be fired from a cannon
A bullet is a far more general term that actually includes projectiles fired from a small arms firearm, or any small arms like Miss Fortune's handguns. Her guns are not large enough to be cannons. So because a cannonball is limited to something fired from a cannon, these shots have to be considered bullets. 
I'm pretty sure they're showing off her ult in the ryze cinematic.
https://youtu.be/oGnZk-_R0KQ?t=168
slow it to 50%
looks to be just regular bullets
