Gunner's role

[Captain Cap]

I'm new and upon testing out all the classes I discovered that gunner's boosts never seemed that effective maybe 1 or two but it made me question this, why not be an engineer and take one special ammo rather than dropping the great necessity of the hammer and fire extinguisher. Is there anything more to the gunner or do I not realize the potential and strategy behind the special ammo or are gunners just known to be useless? As a rookie just trying to put a ship of my friends together, you could say I'm a bit confused to the whole topic.

[sparklerfish]

This has been a hotly contested issue for a long time and there's currently another thread about it going on if you're interested in reading some perspectives. 

https://gunsoficarus.com/community/forum/index.php/topic,5048.0.html

[Omniraptor]

I would say use engineer until you are confident with the simple builds like gat/mortar pyramidion. Then you can branch out into something more specialised, either decide to stick with buff engineer or switch to gunner.

Specifically, do what the captain tells you.

[Alistair MacBain]

Gunners can be effective and better than a third engineer. But those situations/builds are rare.
Guns that profit from gunners are: hwacha, hcarro, hflak,lumberjack, hades, mine ...
Some other guns can utilize gunners aswell but I wouldnt bring a gunner in most cases. Even for the mentioned guns I sometimes tend to rather have a engineer than a gunner.
A standard gat/mortar doesnt need a gunner. You can take one ammo and a buffkit and get more from your gun than any gunner.

[Wundsalz]

Many guns are indeed handled better by buff-engineers than by gunners. Here's a quick reference table, taken from this guide, showing some recommended loadouts for specific guns:

brackets (AMMO) - secondary, often situational pick
Rating:
dark green: best performance
light green: good performance with minor drawback compared to the other class
yellow: inferior to the other class, but viable
red: severe drawbacks compared to the other class

Note that the table only covers the raw damage output. The superior maintenance quality of engineers isn't even taken into consideration there.

[HamsterIV]

On ships with multiple gun combos like the artemis/gat-morter junker gunners can bring the optimal ammo for more than one gun. Also as mentioned before some guns benefit from multiple ammo types. One of the more important rolls of the gunner is to always be shooting. If a ship is uncoordinated it helps to have a little reminder that at least one person should be shooting back at the enemy. A well coordinated ship might be able to operate more efficiently with a 3rd engineer instead of a 2 engie 1 gunner setup, but if nobody is communicating players usually fall back on "Man with bullet shoot, man with wrench fix".