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Home » U-Boat Weapons » Deck Guns

Deck Guns

U-boat deck gun U-boat crews shell a British tanker

The deck gun was principally intended as a defensive weapon against small surface vessels, for which the torpedo was not a suitable weapon. During World War I however, it was discovered that deck guns were quite effective when used against stragglers and helped save scarce torpedoes. During World War II, as convoys became better protected, and merchantmen began to be armed with makeshift defensive guns, the deck gun was used less frequently. Eventually, BdU phased them out, though some U-boats still retained the deck guns.

There were two standard deck guns during World War II; the 8.8cm (on Type VII) and the 10.5cm (on Type IX). The U-boat however, was a poor gun platform since it rolled a lot, and ocean waves frequently washed over, making the gun platform slippery and hazardous. To prevent the crews from being washed over, they were fastened with life lines. A further factor was deck guns had no range finders, so engagements had to be done at close range. Depending on sea and weather conditions, it was also not possible man the deck gun at all times. The deck gun also contributed much to hydrodynamic resistance, slowing the underwater speed and increasing crash dive time. Indeed, deck gun engagements made the U-boat very vulnerable; since the gun and ammunition had to be secured and the crew had to get below deck, all of which meant that it took much longer than usual to submerge.

Three men operated the deck gun gunner, layer and loader, usually under the supervision of the second watch officer. A chain of men were required to bring the ammunition from below the control room floor, then up the conning tower and onto the upper deck. A small watertight locker placed near the gun held a few more rounds ready for use, providing an advantage during the first few vital seconds of engagement. The rate of fire with a good crew was 15 to 18 rounds per minute.

U-boat deck gun U-boat deck gun

8.8cm Schiffskanone (Antiship Cannon)

The naval 88mm gun was not the same as the famous 88mm of the German Army. Installed on the Type VIIs, the ammunition was a single unit round (projectile and cartridge) and weighed about 30 pounds (13.7kg). Mounted on a platform just ahead of the conning tower, it had identical controls on both sides, so the crew of two could operate it from either side.

10.5cm Schiffskanone (Antiship Cannon)

The 105mm gun was installed on the Type IA and Type IX U-boats. It had an improved range and was more powerful than the 88mm, with each round weighing around 51 pounds (23.3kg). It shared the identical gun platform with the 88mm and had no gun shield.

8.8cm deck gun
A Type VII U-boat on Artic patrol. The freezing weather has covered the 8.8cm gun with ice.

U-boat Deck Gun Specification
  88mm Antiship Cannon 105mm Antiship Cannon
Used In Type VII Type IA, IX XB
Caliber 88mm (3.46in) 105mm (4.13in)
Traverse 360 degrees 360 degrees
Elevation -4 to +30 degrees -3 to +30 degrees
Breech Semi Automatic Semi Automatic
High Explosive
Muzzle Velocity
Armor Piercing
Star Shell

700m per second



785m per second



U-995 German Type VIIC U-Boat

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