Editing The Empire (Warhammer Fantasy) (section)

===BIG Guns===
Cannons, however, are what ultimately killed the tercio. As field artillery got better and better, the tercio, a tightly packed group of men, became easier and easier targets. The blocky tercio evolved into the flat lines of Napoleonic warfare so that one would need a flanking cannonball (enfilade) to get a whole rank of soldiers. The Empire's cannons are muzzle loaders and muzzle loaders (given that the ball speed is relatively low) are measured by the weight of their shot. Modern guns, because speed is more important and because muzzle size no longer correlates to shell weight, generally use muzzle size. The British were slow to swap over, which is why the "17 pounder" and "88mm" fought against each other in [[World War II]]. Given the size of a "great cannon", it can be estimated that Empire field guns shoot between a 68-100 pound ball, which is huge, but they have to shoot monsters with them so there we are.

Empire cannons are pre-Gustavus Adolphus, a Swedish king who revolutionized warfare by making his army the most artillery happy in the world by using a lighter cannon. He stopped using everything bigger than 3 pounds (24 pounds if you include his few siege guns) so his army could move faster as the really heavy guns would not slow them down, fire more often because the guns were lighter, and - more importantly - he used a lot more of them. How much more? Almost 6 times as many as his enemies. In one battle, despite being heavily outnumbered, he fired six times for every one of his enemy and won massively. That said, the Empire could be justified in using a heavier ball because Gustavius, badass that he was, did not have to fight [[Bloodthirster]]s. As for their mortars: not much to say, the Empire often neglects their historical use (siege breakers), but otherwise they're fairly accurate (artillery puns!).

Alternate take: The Empire lives in a post- Gustav the Great world, as its great cannons are considered their siege equipment which as contemporary in our world for the period were essential for campaign and as such are able to be limbered up and moved while still powerful enough to breach most fortifications, as most smaller siege guns were at this time. In times prior and for significantly well developed fortifications it required much larger siege cannons which had to be assembled on sight. Ever wondered why a cannon maker in older total wars is called a bell foundry? Because churchbell makers went from church to church casting the massive, often half ton bells on site, and as such were the only people with mobile metalcasting techniques of the quality needed for cannon, and kings put them to work. 
The light, mobile and tactically adept field guns can be seen as the helblaster volley gun, which fires shot larger than handgunner rounds but not cannon sized, tactically offering a canister shot like effect but with likely easier to write tabletop rules instead of "draw a 25 degree angle out from the cannon muzzle. Everything in that range is dead." 
The reason you cant 1:1 with the real world in this situation is because as stated above, the nature of monsters and how that would change the battlefield. Just the change from "very fragile, frightened humans" to "Massive unflinching beasts who can take a cannon shot without dying automatically" would alter things radically, one would assume.
Back on topic now.

On the subject of guns, the Helstorm Rocket Battery is based on the Congreve rocket. They were invented by William Congreve (much like the Empire, real weapons tended to get named after their inventors). They were based on rockets stolen when the British conquered Mysore. Just like the Imperial rockets, Congreve rockets used a big stick to stabilize themselves in flight. The rockets were used from 1806 until 1850 when they were replaced with Hale rockets that spun themselves in flight so they did not need the stick. They could also be inspired by some rare renaissance organ guns with multiple decks, just having their gun barrels swapped out with rocket mounts. Or maybe even the Korean Hwacha, which was a multiple rocket launcher on wheels from the 15th.

[[File:Helblaster_irl,_swiss_volley_gun,_1640.PNG|A Helblaster Volley Gun in real life.|right|thumb]]
Helblasters are based on some volley guns that were made in small quantities during the late 16th and early 17th century. Just like the real one pictured, it works by having multiple barrels divided by decks which can be turned around a shared rotation axle. From the video game TWW it can be seen to be up-gunned from its real life counterpart to be a sort of contemporary of the dwarven organ gun, as it fires small yet still cannon sized shells (Anything greater than 20mm/.79" is a cannon by classification, fyi)