6-inch/30-caliber gun

The 6"/30 caliber gun Mark 1 (spoken "six-inch-thirty-caliber") were used for the primary battery of the United States Navy's dispatch vessel Dolphin with the Mark 2 being used in the secondary batteries for its "New Navy" protected cruisers Atlanta, Chicago, and Boston and the Mark 3 used for the primary and secondary batteries in the succeeding early protected cruisers in addition to secondary batteries in the "Second Class Battleships" Maine and Texas.[1][2]

6"/30 caliber Mark 1, 2, and 3
Atlanta, 6-inch/30 caliber gun.
TypeNaval gun
Place of originUnited States
Service history
In service1885
Used byUnited States Navy
Wars
Production history
DesignerBureau of Ordnance
Designed1883
ManufacturerU.S. Naval Gun Factory
No. built
  • Mark 1: 1
  • Mark 2: 20
  • Mark 3: 109
VariantsMark 1, Mark 2 Mod 1 – Mod 3, Mark 3 Mod 0 – Mod 9
Specifications
Mass
  • Mark 1: 11,010 lb (4,990 kg) (without breech)
  • Mark 2: 10,430 lb (4,730 kg)
Length
  • Mark 1: 189.7 in (4,820 mm)
  • Mark 2: 193.53 in (4,916 mm)
  • Mark 3 Mod 0 and Mod 3: 196 in (5,000 mm)
  • Mark 3 Mod 1: 226 in (5,700 mm)
  • Mark 3 Mod 2 and Mod 8: 256 in (6,500 mm)
Barrel length
  • 30 Caliber: 180 in (4,600 mm) bore (30 calibers)
  • 35 Caliber: 210 in (5,300 mm) bore (35)
  • 40 Caliber: 240 in (6,100 mm) bore (40)
Shell
Caliber6 in (152 mm)
Elevation
  • Mark 3: −7° to +12° (early units)
  • Mark 3: −10° to +12° (later units)
Traverse−150° to +150°
Rate of fire
  • As commissioned: 0.66 rounds per minute (bag guns)
  • After 1906: 7.3 rounds per minute (bag guns)
  • As commissioned: 1.5 rounds per minute (case guns)
  • After 1906: 7.6 rounds per minute (case guns)
Muzzle velocity
  • 1,950 ft/s (590 m/s) 30 caliber
  • 2,000 ft/s (610 m/s) 35 caliber
  • 2,150 ft/s (660 m/s) 40 caliber
Effective firing range
  • 9,000 yd (8,200 m) at 15.3° elevation
  • 18,000 yd (16,000 m) at 30.2° elevation

Design

The 6-inch/30 caliber Mark 1, 2, and 3 guns were developed before the Spanish–American War and still used black powder or brown powder, in later years they were not considered strong enough to withstand the higher chamber pressures generated by the newer smokeless powder adopted around 1898 and were obsolete before the start of World War I.[1]

The Mark 1, gun No. 1, was constructed of tube, jacket, 16 hoops, an elevating band and integral trunnions with a screwed on muzzle bell. The Mark 2 also trunnioned with the Mark 2 Mod 1 only having 10 hoops, jacket, and chamber liner and the Mod 2 the same but with a full-length liner. All Mark 1 and Mark 2 guns were constructed to a length of 30 calibers. In 1895 all Mark 2s were ordered to be converted to rapid-fire, fixed ammunition. This was done in 1898–1902 with gun No. 2 being delivered in November 1898 for use in Atlanta.[1][2]

The Mark 3 was trunnioned as the Mark 1 and Mark 2, but was built in three different caliber lengths, 30, 35, and 40, in eight different Mods, Mod 0 – Mod 6 and Mod's 8 and 9. Mod 0 was 30 caliber with Mod 1 being 35 caliber. All 30 and 35 caliber Mods had a liner, 10 hoops, and a jacket. Mod 2 was 40 caliber with only eight hoops. Mod 3 was again 30 caliber but introduced the use of case (semi-fixed) ammunition. The Mod 4 was experimental in that it eliminated the trunnions and used a threaded sleeve. Mod 5s were reworked Mod 1s making them capable of handling case ammunition. As with the Mod 5 the Mod 6 were Mod 2s reworked to handle case ammunition. The Mod 7 was skipped and no drawings exist for this Mod. The Mod 8 was another Mod 2 rework, this time removing the trunnions and using a threaded sleeve. The last Mod was the Mod 9, using a Mod 3 gun and giving it a full-length liner.[1][2]

Ship Gun Installed Gun Mount
USS Dolphin (PG-24) Mark 1: 6"/30 caliber Mark 1: 1 × shifting pivot
USS Atlanta (1884) Mark 2: 6"/30 caliber Mark 2: 6 × muzzle pivot mount
USS Boston (1884) Mark 2: 6"/30 caliber Mark 2: 6 × muzzle pivot mount
USS Chicago (1885) Mark 2: 6"/30 caliber Mark 2: 8 × muzzle pivot mount
USS Maine (ACR-1) Mark 3: 6"/30 caliber Mark 3: 6 × central-pivot
USS Texas (1892)
  • Mark 3: 4 × 6"/30 caliber
  • Mark 3: 2 × 6"/35 caliber
 Mark 4: 6 × central-pivot w/single-piece slide
USS Newark (C-1)
  • Mark 3: 6"/30 caliber (as built)
  • Mark 3: 6"/40 caliber (refit 1901–1902)
 Mark 3: 12 × central-pivot
USS Charleston (C-2) Mark 3: 6"/30 caliber Mark 3: 6 × central-pivot
USS Baltimore (C-3) Mark 3: 6"/30 caliber Mark 3: 6 × central-pivot
USS Philadelphia (C-4) Mark 3: 6"/30 caliber Mark 3: 12 × central-pivot
USS Columbia (C-12) Mark 3: 6"/40 caliber Mark 3: 2 × central-pivot
USS Minneapolis (C-13) Mark 3: 6"/40 caliber Mark 3: 2 × central-pivot
USS Yorktown (PG-1) Mark 3: 6"/30 caliber Mark 4: 6 × central-pivot w/single-piece slide
USS Petrel (PG-2) Mark 3: 6"/30 caliber Mark 4: 6 × central-pivot w/single-piece slide
USS Concord (PG-3) Mark 3: 6"/30 caliber Mark 4: 6 × central-pivot w/single-piece slide
USS Bennington (PG-4) Mark 3: 6"/30 caliber Mark 4: 6 × central-pivot w/single-piece slide

Preserved weapons

At least five guns of this type are preserved:

See also

Weapons of comparable role, performance and era

Notes
  1. Navweaps 2015.
  2. Friedman 2011, pp. 179–180.
  3. Hartshorn 2015.

References
Books
  • Friedman, Norman (2011). Naval Weapons of World War One. Seaforth Publishing. ISBN 978-1-84832-100-7.
Online sources

Further reading
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