21 cm/45 (8.27") SK L/45
Updated 06 June 2015

Used afloat only on the Armored Cruiser Blücher which was sunk at the World War I battle of Dogger Bank.  After her sinking, four reserve guns were given to the German Army.

During World War II these guns were used as coastal artillery.  They were then supplied with a better ballistically shaped shell and with a larger propellant charge for increased range.

Constructed of A tube, two layers of hoops and a jacket.  Used the Krupp horizontal sliding wedge breech block.  About 16 guns were made.

Actual bore diameter was 20.93 cm (8.24").


Blücher as she appeared pre-war as a gunnery training ship
Bain News Service Photograph
Library of Congress Photograph ID LC-DIG-ggbain-17348


One of the wing turrets on SMS Blücher
The gun barrel below is a 15 cm/45

Gun Characteristics
Designation 21 cm/45 (8.27") SK L/45
Ship Class Used On Blücher
Date Of Design about 1905
Date In Service 1909
Gun Weight 16,156 lbs. (16,400 kg)
Gun Length oa 370.9 in (9.420 m)
Bore Length 347.5 in (8.826 m)
Rifling Length 292.5 in (7.430 m)
Grooves (60) 0.79 in D x 0.266 in W (2.0 mm D x 6.76 mm W)
Lands 0.165 in (4.2 mm)
Twist Increasing RH 1 in 45 to 1 in 30 at the muzzle
Chamber Volume 3,033 in3 (49.7 dm3)
Rate Of Fire 4 - 6 rounds per minute
Type Separate
Projectile Types and Weights World War I
   AP L/3,1 - 238 lbs. (108 kg)
   HE L/3,1 - 238 lbs. (108 kg)

World War II
   AP L/3,1 - 238 lbs. (108 kg)
   HE L/4,3 base and nose fuze - 250 lbs. (113.5 kg)

Bursting Charge AP L/3,1 - 7.67 lbs. (3.5 kg)
HE L/3,1 - 15.18 lbs. (6.9 kg)
Others - N/A
Projectile Length AP L/3,1 - 25.6 in (65 cm)
HE L/3,1 - 25.6 in (65 cm)
HE L/4,3 - 35.5 in (90 cm)
Propellant Charge
(see Note 3)
World War I
   77.3 lbs. (35.1 kg) RP C/06

World War II

Cartridge Case Type, Size and Empty Weight Brass, 210 x 836 mm, N/A
Muzzle Velocity 2,953 fps (900 mps)
Working Pressure 20.2 tons/in2 (3,175 kg/cm2)
Approximate Barrel Life N/A
Ammunition stowage per gun 85 rounds

1) The World War II HE round was a special coastal artillery projectile with both base and nose fuzes.  This projectile was of better ballistic shape than the earlier AP projectile.

2) Actual Projectile designations were as follows.
   AP L/3,1 - Psgr. L3,1
   HE L/4,3 base and nose fuze - L/4,3 Bdz u. Kz

3) These guns, like most large caliber German guns of this era, used a "fore charge" which was propellant in a double bag silk case and a "main charge" which was propellant in a brass case.  The brass case helped to seal the breech of the gun.  Fore charge was 12.3 lbs. (5.6 kg) and main charge was 65.0 lbs. (29.5 kg).

With 238 lbs. (108 kg) AP L/2,9
With 250 lbs. (113.5 kg) HE L/4,3
Range @ 30 degrees
(Max. elevation of turret)
20,900 yards (19,100 m)
Range @ 45 degrees
(Coastal Artillery)
31,700 yards (29,000 m)
Mount / Turret Data
Designation Two-gun turrets
   Blücher (6):  DrL C/06
Weight  195 to 197 tons (198 to 200 mt)
Elevation -5 / +30 degrees
Elevation Rate 4 degrees per second
Train Forward and Aft Turrets:  about -150 / +150 degrees
Beam Turrets:  about +30 / +150 degrees
Train Rate 3.5 degrees per second
Gun recoil 20.5 in (52 cm)

1) All but the forward wing turrets fed from common projectile/propellant ammunition magazines with two fixed hoists passing projectiles and main charges to a handling room below the gunhouse.  Forward wing turrets differed from the other turrets in that they were fed from the ammunition spaces located beneath the rear wing turret via a centerline conveyor belt.  This fed the wing turret handling rooms via inclined hoists, one for projectiles and one for main charges.

2) Fore charges were passed into the handling room through openings in the barbette.  Upper hoists revolved with the gunhouse.  Each gun had a single hoist which fed both projectiles and main charges to the gun while the fore charge was supplied by auxiliary hoists located between the main hoists.  The working chamber held ready ammunition, storing either 38 APC or 34 HE, 26 main and 52 fore charges.  These allowed the guns to fire at about six rounds per minute until these were used up.  Afterwards, the ROF was about 4 to 5 rounds per minute.

3) Guns were individually sleeved, but could be coupled together.

4) Gun axes were 70.9 in (180 cm) apart.

5) Armor thickness given in "Naval Weapons of World War One" by Norman Friedman:

    Face:  7.1 in (18 cm)
    Sides:  5.5 in (14 cm)
    Rear:  6.2 in (15.8 cm)
    Roof:  2.4 to 3.1 in (6 to 8 cm)

Data from
"Naval Weapons of World War Two" by John Campbell
"Naval Weapons of World War One" by Norman Friedman
"German Warships 1815-1945" by Erich Gröner
"German Warships of World War I" by John C. Taylor
Tony DiGiulian's Personal Data Files
Page History

29 February 2008 - Benchmark
28 March 2010 - Added side view of Blücher
22 May 2012 - Updated to latest template
25 November 2012 - Added details about guns, ammunition and mountings
06 June 2015 - Added weights of main and fore charges, minor other changes