On my lego HMS Warrior, I used 8 normal cannons (68pounders) and 4 custom made guns (110pounders). These guns were the most advanced in their day. They were specially designed to fire through the plates of ironclads such as the french warship "La Gloire". They were also breech-loaders so they could be loaded from the back with out having to pull the gun back and load it from the front.
About this creation
Here are some instructions on how to make a lego 110pounder gun.
first, you need these pieces
First, place the 2 small cylinders on top of each other.
Next, add a big clyinder on top of them and then a 2x2block on top of that.
Then add the "bullet" shaped piece on top of the block and a 2x1 block on top of the bullet shape.
then, beneath the 2x1 block, add 2 1x1 side pieces.
On the side of those pieces, add two low 2x1 pieces.
Then add the wheels beneath the low 2x1 piece.
At the back, add a big cylinder piece.
Finally, add the 2 miniture cylinders on the back.