254mm 45 caliber Pattern 1891

254mm 45 caliber Pattern 1891
A twin gun turret aboard the battleship Rostislav.
Type	Naval gun Coastal artillery
Place of origin	Russian Empire
Service history
In service	1897-1930
Used by	Russian Empire Empire of Japan
Wars	Russo-Japanese War World War I
Production history
Designed	1892
Manufacturer	Obukhov State Plant
Produced	1897
Specifications
Weight	24–27.6 t (26.5–30.4 short tons)
Length	11.4 m (37 ft 5 in)
Barrel length	11 m (36 ft 1 in)
Shell	Separate loading bagged charge and projectile
Shell weight	225 kg (496 lb)
Caliber	254 mm (10.0 in) 45 caliber
Traverse	-135° to +135°
Muzzle velocity	692 m/s (2,270 ft/s)
Maximum firing range	20.4 km (12.7 mi) at +30°

The 254mm 45 caliber Pattern 1891 was a Russian naval gun developed in the years before the Russo-Japanese War that armed coastal defense ships and pre-dreadnought battleships during the Russo-Japanese War and World War I. Guns salvaged from scrapped ships found a second life as coastal artillery. It is believed none were in service during World War II.

The 254mm 45 caliber Pattern 1891 was the product of an agreement between the Imperial Russian Army and Navy to standardize calibers and ammunition during 1892. The gun originally envisioned in 1892 was a 228 mm (9.0 in) 45 caliber gun, with a 192.5 kg (424 lb) shell, a muzzle velocity of 763 m/s (2,500 ft/s) and a brown powder propellant charge. In 1893 a new scaled up 254 mm (10.0 in) 45 caliber gun, weighing 22 t (24 short tons), with a 225 kg (496 lb) Army shell, a muzzle velocity of 914 m/s (3,000 ft/s) and a smokeless powder propellant charge was specified. The weights and dimensions of the new gun were expected to be as close to the original specifications as possible to remain compatible with the ships they were intended to arm. This compromise in design objectives was to have negative effects on the finished product.

Testing in 1895 found that the guns were too lightly built to be able to achieve the specified muzzle velocity even with lower power brown powder. Stress cracks were found and the barrels already produced had to be sent back to the factory to be strengthened and weight grew from 24 t (26 short tons) to 27.6 t (30.4 short tons). The strengthened barrels were not ready until 1897 and after testing in 1899 a lower muzzle velocity of 692 m/s (2,270 ft/s) with reduced charges was accepted. Barrel life was estimated to be 250 rounds.

The elevation range for the gun turrets of the Ushakov, Seniavin, Rostislav was -5° to +15°. The elevation range for gun turrets of the Apraksin, Pobeda, Peresvet and Oslyabya was -5° to +30°. The rate of fire was 120 seconds for Admiral Seniavin, 107 seconds for Ushakov, 93 seconds for Apraksin, but only 80 seconds for Peresvet, Oslyabya and Pobeda.