United States of America
6"/30, 6"/35 and 6"/40 (15.2 cm) Marks 1, 2, 3, 4 and 7
Updated 25 December 2008
These guns had many similarities in their construction, but, as in most of the "New Navy" gun development, there was much experimentation with different barrel lengths, rifling and ammunition types.

The Mark 1 was the original 6" (15.2 cm) BL gun used on the "ABCD" squadron (Atlanta, Boston, Chicago and Dolphin).  It consisted of A tube, jacket, 16 hoops and one elevating band with integral trunnions and a screwed on muzzle bell.  Mark 2, 3 and 4 had 10 hoops.  There was only one Mark 7 gun, which was a Mark 4 modified to take bag ammunition.

The 30 caliber weapons were primarily used on cruisers while the 35 and 40 caliber weapons were used on battleships.

Besides the guns with "Mark" number designations, there was a single early wire-wound 6"/30 (15.2 cm) prototype gun that was not assigned a Mark number and which apparently did not enter service.

Almost all of these guns were condemmed shortly after World War I.
WNUS_6-30_mk1_Atlanta_pic.jpg

6"/30 (15.2 cm) gun on the Cruiser Atlanta circa 1895
Note three-motion breech mechanism and Mark 2, Muzzle Pivot Mount inclined mounting
Detroit Publishing Company Collection Photograph
Library of Congress Photograph ID LC-USZ62-60234
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Click here for additional pictures
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Gun Characteristics
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Designation 6"/30 (15.2 cm) Mark 1 [Bag]
6"/30 (15.2 cm) Mark 2 [Separate]
6"/30 (15.2 cm) Mark 3 Mod 0, Mod 3 and Mod 4 [Bag]
6"/35 (15.2 cm) Mark 3 Mod 1 [Bag]
6"/40 (15.2 cm) Mark 3 Mod 2 [Bag]
6"/35 (15.2 cm) Mark 3 Mod 5 [Separate]
6"/40 (15.2 cm) Mark 3 Mod 6 and 8 [Separate]
6"/30 (15.2 cm) Mark 3 Mod 9 [Separate]
6"/40 (15.2 cm) Mark 4 [Separate]
6"/40 (15.2 cm) Mark 7 [Bag]
Ship Class Used On
(see Note 2)		 "New Navy"
   6"/30 (15.2 cm):  Dolphin, Chicago, Atlanta and Boston

Second Class Battleships
   6"/30 (15.2 cm) Maine and Texas
   6"/35 (15.2 cm) Texas

Coastal Battleships
   6"/40 (15.2 cm):  Indiana (B-1), Iowa (B-4) and Illinois (B-7) classes

Cruisers
   6"/30 (15.2 cm):  Newark (C-1), Charleston (C-2), Baltimore (C-3), Philadelphia (C-4) and San Francisco (C-5) classes
   6"/40 (15.2 cm):  Cincinnati (C-7) class

Gunboats
   6"/30 (15.2 cm):  Yorktown (PG-3) class
Date Of Design 1883
Date In Service 1885
Gun Weight Mark 1:  11,010 lbs. (4,994 kg) without breech
Mark 4:  13,370 lbs. (6,065 kg) without breech
Others:  N/A
Gun Length oa N/A
Bore Length 30 Caliber:  180 in (4.572 m)
35 Caliber:  210 in (5.334 m)
40 Caliber:  240 in (6.096 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist Mark 1:  Increasing RH 1 in 180 to 1 in 30
Mark 2:  Increasing RH 1 in 40 to 1 in 30
Mark 3:  Increasing RH 0 to 1 in 30
Mark 4:  Increasing RH 0 to 1 in 35
Mark 7:  Increasing RH 0 to 1 in 25
Chamber Volume N/A
Rate Of Fire
(see Note 1)		 Bag Guns
   As commissioned:  0.66 rounds per minute
   After about 1906:  7.3 rounds per minute

Separate Guns
   As commissioned:  1.5 rounds per minute
   After about 1906:  7.6 rounds per minute
Notes:

1) In 1897 the 40 caliber gun (bag ammunition) was timed at one shot every 90 seconds and the 40 caliber RF gun (separate ammunition) at one round every 40 seconds.  This was greatly improved by more careful loading practices and better training so that by 1907 the above rates (8.2 seconds and 7.9 seconds, respectively) were achieved.

2) The Second Class Battleship Texas carried four 6"/30 (15.2 cm) and two 6"/35 (15.2 cm) weapons, an unusual mixing of calibers.
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Ammunition
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Type Bag and Separate
Projectile Types and Weights AP - 105 lbs. (47.7 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge 18.8 lbs (8.5 kg)
Muzzle Velocity 30 Caliber:  1,950 fps (594 mps)
35 Caliber:  N/A
40 Caliber:  2,150 fps (655 mps)
Working Pressure 30 Caliber:  13.3 tons/in2 (2,100 kg/cm2)
Others:  N/A
Approximate Barrel Life N/A
Ammunition Stowage per gun Texas:  100 rounds
Indiana:  100 rounds
Illinois:  200 rounds
Cincinnati:  150 rounds
Others:  N/A
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Range
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Elevation With 105 lbs. (47.7 kg) Shell
Range @ 15.3 degrees
MV:  1,950 fps (594 mps)		 9,000 yards (8,230 m)
Range @ 30.2 degrees
MV:  2,150 fps (655 mps)		 18,000 yards (16,460 m)
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Mount / Turret Data
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Designation
(see Notes 2 and 3)		 "New Navy"
   Dolphin (1):  Mark 1, Shifting Pivot
   Atlanta (6), Boston (6) and Chicago (8):  Mark 2, Muzzle Pivot Mount

Second Class Battleships
   Maine (6):  Mark 3, Central-pivot
   Texas (6):  Mark 4, Central-pivot with single-piece slide

Coastal Battleships
   Indiana (4):  Mark 5, Central-pivot
   Illinois (14):  Mark 6, Pedestal Mount (modernized to Mark 7 by 1905)

Cruisers
   Newark (12), Charleston (6), Baltimore (6), Philadelphia (C12) and San Francisco (12):  Mark 3 Central Pivot
   Cincinnati (1):  Probably Mark 6, Pedestal Mount

Gunboats
   Yorktown (6):  Probably Mark 4
Weight  With 6"/30 (15.2 cm):  21,856 lbs. (9,065 kg)
With 6"/40 (15.2 cm):  25,430 lbs. (11,535 kg)
Elevation Mark 3:  -7 / +12 degrees for early units, -10 / +12 degrees for later units
Others:  N/A
Elevation Rate Manual operation, only
Train about +150 / -150 degrees
Train Rate Manual operation, only
Gun recoil N/A
Notes:

1) The Mark 5 was the first rapid fire (RF) recoil mount in the USN.

2) Mounting designations shown above for Maine, Texas, Indiana and the cruisers represent my best guess based upon information in the references below and from examination of photographs.

3) Dolphin was originally armed with one 6"/30 (15.2 cm) gun, but this was quickly removed and she was rearmed with three 4 in (10.2 cm) in 1898 and by 1916 she carried one 4 in (10.2 cm) and two six-pounders.
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Data from
"US Battleships:  An Illustrated Design History," "US Cruisers:  An Illustrated Design History" and "US Naval Weapons" all by Norman Friedman
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"United States Naval Guns:  Their Marks and Modifications" Ordnance Pamphlet No. 127, December 1916, Second Revision June 1924
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Gene Slover's Navy Pages