Generally speaking a mine launcher build is fairly easy to beat. Of course if they have good gunners the difficulty goes up dramatically. Mines have a very specific range. This range can be changed with a proper use of gunner tools.
https://gunsoficarus.com/community/forum/index.php/topic,3059.0.htmlThe mine launcher can go from about 80 meters to about 340 meters (with tools, although in practice these numbers seem a bit off). As far as I can tell, they'll explode on 'impact', but both ships and the mines have larger hitboxes than they seem to. So it's really about 20-30 meters or so (closer than it sounds). Considering that ships are volumes, this actually gives quite a bit of room for a good gunner. You're not actually trying to strike the ship directly, but the area around the ship.
Knowing this, a gunner on a mine launcher is taking into account a lot of information. They need an estimate on the distance (usually through experience), their velocity, and the target's velocity. (velocity includes direction).
Personally I'm a one mine launcher kind of person, but that puts a lot of pressure on the gunner to get hits. A munker (and other ships with lots of mine launchers) are usually reducing the need for accuracy with sheer numbers of mines. Creating whole fields. This makes it difficult to chase them. And once you start getting hit, you'll likely continue to get hit (you'll take damage and suffer the impact, often slowing you down and making you an easier target).
To beat a ship who's primary weapon is a mine launcher, you have two options. Option one is stay out of their range. This means getting too close to them, or too far for their mines to explode on you. This can be a problem with munkers in particular, since they don't really have a blind spot, and the mine launchers have a large turning arc.
Assuming you have a gat/mortar build and not something long range, you should try to stay just inside of the gat range and pepper them. Ideally you'll be just out of mine range. You likely won't kill them, but they won't be able to kill you either. If they start trying to chase, just back up. They'll have trouble going around their own mines. At a certain point you'll actually want to change directions and charge at them. They're likely still using lesmok and trying to get you at range. Right when you're just about in lesmok range, burst forward. You might take a mine hit, but if you time it right it will just hit your ship. Now they're reloading and you're already ramming them. Unless they have lochnagar, they're very unlikely to hit you; and lochnagar comes with the downside of reducing the aoe size. So even when they start getting you, it's going to mostly be hull damage. Your engines and guns should be relatively fine.
But assuming you're that close, they should be destroyed in a relatively fast manner. The mines use impact damage, so things like moonshine can be used to reduce the amount of rotation to your ship. If they can't turn you or slow you down, they'll have a hard time keeping you in their active range.
Option two is probably easier. Ignore them and go for their ally. A mine ship by nature is more defensive. If you hug their ally, they can't mine as effectively for fear of killing their own team. Of course some players could care less about that. However, going for their ally also causes them to try and move in on you, instead of you chasing them. This again makes it easier to charge them and take them down, instead of trying to follow them through a mine field.
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tldr:
Be aware of their effective ranges. Kerosene is you friend. Don't be afraid to take a mine or two to get in their face. You can always go for their ally.