Cannons and bells are not made of the same metal, nor are they the same thickness. Also not all metal that cannons are made of actually rust, so be careful with that as well. Try to find some reference of cannons and sculpt from that so you get more believable results.
Be careful with the detail you are sculpting into the cannon barrel because it is starting to look like concrete. I am not sure what you are looking at for reference, but metal tends to chip and scratch which are fairly subtle compared to what you sculpted in there. The wood looks really nice though, good job with that.
Thanks for the feedback! Oh! Of course, I'll keep that in mind :) I didn't really have a reference, I just thought of how old cast iron pans and cast church bells look and freestyled it from memory. I did the same with the wood. The look I was going for was old and rusty with battle scars, like maybe a cannon ball hit it…