The early 17th century saw numerous types of cannon in every size and configuration between the major nations of the day. There was nothing approaching standardization, but that is something we need for our purposes. Let's jump right in: cannon break down into three categories based on trajectory of fire.
- Guns have a level firing arc and are used for direct fire.
- Cannon fired at a roughly 45 degree angle and are used to shoot larger projectiles at targets behind obstructions.
- Mortars have a high angle of fire to deliver indirect fire over walls.
While these were primarily siege weapons, guns and howitzers were employed as field artillery, especially after Gustavus Adolphus proved their worth near the end of the 30YW. Cannon ranged in caliber from 4-inch field pieces to 9-inch behemoths firing 80lb shot! Here's a convenient breakdown:
That might be a lot of artillery, but it covers pieces designed for sieges, field use, and medium sized cannon that could be used for both. To simplify matters, the list could be condensed to just a Siege and Field version of Gun and Cannon and just the big Mortar.
In regards to shot, there were plenty of choices. Solid iron shot was used to puncture holes in walls as well as to knock out opposing cannon with enfilade fire. In the field, solid shot wrecked havoc on deep pike formations as it mowed down men.
Mortars used stone balls since they were not employed to break through fortifications. In fact, mortars were designed to only use stone or explosive shot; loading an iron ball and extra powder into a mortar would result in a dead cannon crew. The Bombard's stats look to be incorrect based on the other values, but that is because it is a short, stout weapon (think of a cauldron rather than a cannon) reminiscent of 16th century technology.
Explosive shot was made by filling a hollow iron sphere with powder. They were lobbed by howitzers and mortars to destroy buildings, earthworks, and for general bombardment.
Chain shot was used in naval artillery for destroying rigging, it consisted of two sub-caliber sized round shots connected with a chain.
Canister shot was employed to a degree in the 17th century. However, they were not standardized shells and more like an improvised shotgun-type blast. Since cannon in the early part of the 17th century were still thought of as a siege weapon first, they saw relatively little use.
This information doesn't provide comprehensive rules for artillery use in battle, but should lay the groundwork for future development. Suffice to say, these pieces have to be very expensive as even the major nations of the day would rarely be able to field more than 50 pieces with their armies. Unless your group is at name-level play, these should remain out-of-reach for the moment.
Although, wheeling cannon into a dungeon would be interesting. One silence spell plus a nice Culverin allows you to get through a dungeon rather quickly. Of course, I expect you to enforce air quality rules for all of that powder going off in a confined area...