Slag- similar effect to Tar Barrel, it should fire a smog cloud from whichever gun its fired from. This is beneficial because not only can you fire it from a rear-end gun, but you can fire it from a front-end gun while running in reverse. The bullet should not be abusable, and should not have as profound as effect as Tar Barrel.
Cloud should last 10 seconds (vs 30s), and the gun should lose half life, so you can't just shoot it constantly (or it'd break down, and you need to reload bullet type).
Sticky Harpoon- Special ammo only for harpoon gun. Meant for hitting allied ships, but dealing less damage, because (...it's a rubber harpoon covered in tar that sticks to ships instead of pierce it? sounds reasonable). Now, instead of the harpoon gun being a niche weapon, it can be used to help allied ships in common situations. For slower allied ships, or ships that have their engines blown, attach yourself and help tow them out of trouble. Or for allies that have their balloons shot down, if you can attach to keep them afloat for a few more seconds while they repair.
To avoid abusing this ammo, the stick should only last 10?? seconds. It should also still do some damage on impact. And slow reload time to prevent just re-attaching repeatedly.
Slug Rounds- Much weaker version of carronade ammunition. Placed on long-range weapons, this can shore up some of the short-range weaknesses by giving a very very weak version of a shotgun. (Not meant to create an all-purpose gun, just gives a very sub-par option for a ship with all long-range weapons).
40% of carronade damage, +recoil, 200m range (as opposed to carronades 400m range)
all percent increases and numbers are just for show, not sure what is good but I just wanted to share the ideas, the numbers can always be tweaked