This has been bugging me for a while.
Let's start off by thinking about the most powerful guns in the game. The best heavy weapon is the lumberjack, no contest. The best light weapon is by far the Hades. The thing is, the main balancing factor of these guns is their limited effective range. A vanilla shot from either can't hit up close because of arming time, and it can't hit distant targets because of the slow projectile speed. If you have one extra ammo type, you can fix one of these (e.g. lesmok for long or loch for close), and the gun's balanced because there's still a certain range that it's useless in.
But what if you have three ammo types?
This is where the gunner gets silly. As an engi you need to pick between range extension, damage increase, or arming distance reduction. With the gunner, you get the whole package. Ever wonder why mercuries and gatlings have become less used in high-level play? It's because a Hades with lesmok can hit at 1500+ metres and still do crazy DPS, while a greased Hades can hit IN GAT RANGE without losing damage (in fact, its DPS increases!). What's the point of having these restrictions on a gun if they're just going to be nullified like that? Don't even get me started about how there's still an extra spot left over for a third ammo type. For the lumber that can mean the addition of charged, burst, or, scariest of all, heatsink.
Other guns are the same. Charged might seem like the only ammo type you need for the heavy flak, but lesmok is so, so much deadlier than people would have you think. Do you know how much damage an unbuffed, lesmok flak shot does to hull? 462. That's almost enough to kill a Junker. Throw in a couple of, say, Artemis shots, and you're killing Pyras and Mobs and Spires in seconds at over 1500 metres. If a gunner gets good enough at switching between lesmok and charged (and loch), there is not a single ship in the game that can survive the onslaught of pure explosive damage.
There is, in my mind, one other glaring issue with the gunner, which concerns general rather than mid to high level play. Let's take a look at the AI: there's an AI engi, and an AI gunner. The AI engi will make full use of their mallet, spanner, and fire tool. The gunner on the other hand will only really use one of its ammo types, and seems to have no idea when it should do so. The AI gunner is therefore entirely useless. What connection does that have to gunners being OP? Well, imagine you start a match with a pilot and an engineer. What AI does the game give you? An engineer and a gunner. You now have one member of the crew who is entirely useless. If you have a pilot and a gunner, on the other hand, the game will give you two AI engineers. Now none of your crew are useless. This strongly encourages people to bring gunners rather than engineers in pub matches with many AI.
Here's what I think should be done to nerf the gunner:
-Lower the gunner's capacity to two ammo types
-Force the gunner to use a clip of vanilla rounds between ammo switches. So for example if I want to switch from lesmok to charged, I'd have to fire the clip of lesmok, fire a clip of vanilla, and then I'd get to load charged in.
-When there are two AI and a gunner on the ship, force one AI to be a pilot. That should be enough to compel people to consider running engi instead.
-Apply a -20% modifier to the number of rounds in a clip loaded by a gunner, partly for the sake of realism. If you're carrying so many different types of heavy bullets around, you can't be expected to take an entire clip.
-As a small buff to go with the previous point, increase the gunner's running speed by 20%.