United States of America
7"/44 (17.8 cm) Mark 1
7"/45 (17.8 cm) Mark 2
Updated 21 July 2012
Used as secondary guns on the last US pre-dreadnought classes.  This caliber was selected as it was considered to be the largest possible given the technology of the time that was suitable for a rapid-fire (RF) secondary gun.

Many guns removed from old battleships were used as mobile land artillery (tractor mountings) during World War I.  The mountings were designed by BuOrd and built by the Baldwin Locomotive Works in Philadelphia, Pennsylvania.  The US Marines ordered 20 of these guns and the Army ordered 34 guns.  18 guns were delivered to the Marines and 20 to the Army prior to the Armistice, but none of these were actually used in France.  One of the tractor mountings still exists and has been restored, as can be seen on the additional pictures page.  An additional number of guns, still in their naval pedestal mountings, were used as railway guns during World War I.

During World War II, a number of the surviving guns were used in emergency coastal defense batteries.  Two of the coastal guns still exist at Ft. Derussy at Pearl Harbor, Hawaii and as of 2006, four more were mounted at Bora Bora, French Polynesia.

In 1908 AP projectiles were fitted with a longer ballistic cap of 7crh which improved their penetration ability at longer ranges.

Mark 1 was a built up gun with Welin breech block and uniform rifling 1/25.  Mark 2 was similar but used a liner and had increasing rifling 0 to 1/25.  It was also one caliber or some 7" (17.8 cm) longer than the Mark 1.  Most guns built appear to have been Mark 2 models.
WNUS_7-45_mk2_Vermont_pic.jpg

USS Vermont B-20 in 1909
A close amidships view of the multiple secondaries used on USN pre-dreadnoughts.  The amidships turrets have 8" (20.3 cm) guns, with 7" (17.8 cm) guns in the hull casemates and 3" (7.62 cm) guns in the superstructure casemates.  Just visible at the far right is one of the main 12" (30.5 cm) turrets.
U.S. Naval Historical Center Photograph # 19-N-4-16-18
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Click here for additional pictures
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Gun Characteristics
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Designation 7"/44 (17.8 cm) Mark 1
7"/45 (17.8 cm) Mark 2
Ship Class Used On Connecticut (B-18) and Mississippi (B-23) Classes
Date Of Design about 1900
Date In Service 1906
Gun Weight 12.8 tons (13.0 mt)
Gun Length oa Mark 1:  316.0 in (8.026 m)
Mark 2:  323.0 in (8.204 m)
Bore Length Mark 1:  308 in (7.823 m)
Mark 2:  315 in (8.001 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist Mark 1:  Uniform RH 1 in 25
Mark 2:  Increasing RH 0 to 1 in 25
Chamber Volume N/A
Rate Of Fire 4 rounds per minute
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Ammunition
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Type Bag
Projectile Types and Weights
(see Notes 1 and 2)		 AP Mark 6 Mods 0 and 1 - 165 lbs. (74.8 kg)
AP Mark 10 Mod 2 - 165 lbs. (74.8 kg)
AP Mark 12 Mods 1 and 2 - 165 lbs. (74.8 kg)
Common - 165 lbs. (74.8 kg)

Field Mark 13 Mods 1 and 2 - 152 lbs. (68.9 kg)
Bombardment Mark 14 Mod 2 - 153.8 lbs. (69.8 kg)
Bursting Charge AP Mark 6 - 4.31 lbs. (2.0 kg) Explosive D
AP Mark 10 - 4.31 lbs. (2.0 kg) Explosive D
AP Mark 12 Mod 1 - 4.0 lbs. (1.8 kg) Explosive D
AP Mark 12 Mod 2 - 3.5 lbs. (1.6 kg) Explosive D
Common - 5.5 lbs. (2.5 kg) Explosive D

Field Mark 13 - 24 lbs. (10.9 kg) Cast TNT
Bombardment Mark 14 - 24 lbs. (10.9 kg) Cast TNT
Projectile Length AP Mark 6 - 23.64 in (60.0 cm)
AP Mark 10 - 23.73 in (60.3 cm)
AP Mark 12 - 23.68 in (60.1 cm)
Common - about 23.64 in (60.0 cm)

Field Mark 13 - 29.58 in (75.1 cm)
Bombardment Mark 14 - 28.84 in (73.3 cm)
Propellant Charge 58 lbs. (26.3 kg) SPD
Muzzle Velocity 2,700 fps (823 mps)
Working Pressure 17.0 tons/in2 (2,680 kg/cm2)
Approximate Barrel Life N/A
Ammunition stowage per gun Connecticut class:  100 rounds
Mississippi class:  111 rounds
Notes:

1) All AP projectiles had almost identical nose shapes, but the designs were very different.  AP Mark 6 had no ballistic cap, but the AP cap was essentially shaped like a thick-walled ballistic cap.  AP Mark 10 had a ballistic cap covering a flat-nosed AP cap.  AP Mark 12 had a ballistic cap covering a concave AP cap.  See sketch at the "additional pictures" link above.

2) Field and Bombardment rounds were developed for Marine and Army artillery units, they were not used on ships.  These had similar projectile shapes, but the Field round did not have a base fuze.

3) Bourrelet diameter for AP Mark 6 was 6.990 inches (17.8 cm).  All other rounds had a bourrelet diameter of 6.985 inches (17.7 cm).
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Range
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Elevation
With 165 lbs. (74.8 kg) AP
MV = 2,700 fps (823 mps)
Striking Velocity
Angle of Fall
3.0 degrees
6,000 yards (5,490 m)
1,810 fps (552 mps)
3.9
4.1 degrees
7,500 yards (6,860 m)
1,635 fps (498 mps)
5.7
15 degrees
16,500 yards (15,090 m)
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Time of flight for MV = 2,700 fps (823 mps)
   6,000 yards (5,490 m):  8.2 seconds
   7,500 yards (6,860 m):  10.8 seconds
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Armor Penetration With 165 lbs. (74.8 kg) AP Shell
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Range
Side Armor
Deck Armor
0 yards (0 m)
9.60" (244 mm)
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6,000 yards
5.21" (132 mm)
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9,000 yards
3.84" (98 mm)
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12,000 yards
3.43" (87 mm)
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Note:  This data is for face-hardened Harvey plates from "Ordnance Data Sheets" of 1905 and is for the older shell design.
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Range
Side Armor
Deck Armor
6,000 yards (5,490 m)
6.3" (160 mm)
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9,000 yards (8,230 m)
4.3" (109 mm)
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12,000 yards (10,920 m)
3.2" (81 mm)
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Note:  This data is from "Elements of US Naval Guns" of 1918 and is for the 7crh projectile at a muzzle velocity of 2,400 fps (732 mps).  Data is corrected for angle of fall and may also refer to harder armor than used for the 1905 data.
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Mount / Turret Data
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Designation Single pedestal type for casemates
   Connecticut (12) and Mississippi (8):  Mark 1 and Mark 2
Weight  25 tons (26 mt)
Elevation -7 / +15 degrees
Elevation Rate N/A
Train about +150 / -150 degrees
Train Rate N/A
Gun recoil Nominal:  19 in (48 cm)
Maximum:  21 in (53 cm)
Loading angle Any angle
Notes:

1) The World War I tractor mounting allowed a maximum elevation of 40 degrees.  At this angle, a maximum range of about 24,000 yards (21,900 m) could be achieved.

2) The railway units used the Mark 2 Mod 3 naval mounting together with a special adapter casting, which both mated the gun pedestal to the railway car and raised the gun muzzle to a safe clearance height above the car.  The casting weighed about 13,000 lbs. (5,900 kg).  This mounting allowed a full 360 degrees of traverse.  The railroad car itself was a drop-frame type that needed to be lowered to the rails and its four outriggers set up before the gun could be fired.  See picture link below.
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Data from
"Naval Weapons of World War Two" by John Campbell
"US Naval Weapons," "US Cruisers:  An Illustrated Design History" and "US Battleships:  An Illustrated Design History" all by Norman Friedman
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"The Engineer" 27 April 1917 as quoted in Warship International No. 1, 1994
USNI Proceedings Vol. 45, No. 7, July 1919
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"Naval Ordnance - A Text Book" revised in 1915 by Lt. Cmdr. Roland I. Curtain and Lt. Cmdr. Thomas L. Johnson
"U.S. Explosive Ordnance:  Ordnance Pamphlet 1664 - May 1947" by Department of the Navy
"Range and Ballistic Tables 1935" by U.S. Department of Ordnance and Gunnery
"Handbook of Ordnance Data No. 1861, 15 November 1918" by United States Army Ordnance Department
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Special help from Charley Seavey
Off-site Resources

Interesting datapage on the tractor mounts, Track-propelled Gun Mk.2 1918 at Landships

Page History

15 August 2008 - Benchmark
29 March 2009 - Fixed typographical error
16 October 2010 - Modified off-site Resources
21 July 2012 - Added a mention of Bora Bora guns