Eli5: How are submarine deck guns able to still be fired after being submerged in salt water?

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Eli5: How are submarine deck guns able to still be fired after being submerged in salt water?

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They’re heavily protected by anti-corrosive paint on the outside, slathered in waterproof grease, and they only submerged with the breech closed and the muzzle plugged. That way, saltwater never got into the inner workings of the gun.

WWII or earlier subs didn’t have much submerged range, at least not the way we think of modern subs. When submerged they ran on electric batteries, so at best you’re talking hours to a few days. I think the best endurance (submerged) would be a type-21 German U-boat, that was something like 75 hrs at ~5knots, and unlike earlier ones it had a snorkel that actually worked. But, the majority of WWII subs could stay submerged for like 15-20 hrs and would have to surface to recharge using the diesel engines. In any case, my point is that subs typically ran on the surface for most of their cruise and submerged only to fight.

So, being on the surface, the problem devolves into typical naval gun maintenance. Stop or plug the barrel of the gun with a tampion, keep it well painted and lubricated and greased and keep the bits that can open (like the breech) closed (they’re gastight already), then keep the gun wrapped in a tarp to keep the majority of the spray off. But you’re still doing a lot of maintenance when surfaced.

Same way as deck guns on any other ship, lots of regular maintenance. Remember that submarines with deck guns were basically surface ships most of the time.

When post-war submarines got significantly greater submerged capabilities (and for the US, working torpedoes), they ditched the deck guns and the crew just stayed inside.

The gun is mechanical not electrical and so fires if properly maintained. Plus the ammo is stored inside the ship so it doesn’t corrode. Drop any gun in water for a few minutes, take it out, shake out the water, load it and it will most likely fire. You can even find video of rifles being fired underwater.

Drachinifel (my YT hero) says it’s by putting a ton of grease on them so they water doesn’t get in the mechanisms. And of course plug everything you can put a plug on.

I add this: you pew pew and when you come back you can remove the gun for maintenance.

And you can install blocks of zinc close to the gun parts, zinc will corrode faster than iron and therefore iron will corrode less. Its basically a decoy for salt. It’s called sacrificial material and it’s done also on ship rudders for example.

But you are spot on, saltwater is not friendly and guns are easy to jam. Consider that war is not that long. Ship may be sunk well before to need heavy maintenance, a good portion of ww2 ships and subs did lived just months.