4-inch/40-caliber gun

4″/40 caliber Marks 1, 2, 3, 4, 5, and 6
Photograph of USS Iowa, 4-inch gun and gunner.
Type	Naval gun Coastal artillery
Place of origin	United States
Service history
In service	1897—1945
Used by	United States Navy
Wars	Spanish–American War Philippine–American War Boxer Rebellion World War I Siberian Intervention World War II
Production history
Designer	Bureau of Ordnance
Manufacturer	Naval Gun Factory American Ordnance Company Bethlehem Steel
No. built	Mark 1: 4 (Nos. 1–3, 6) Mark 2: 2 (Nos. 4–5) Mark 3: 69 (Nos. 7–69, 71, 73, 74, 82, 87) Mark 4: 45 (Nos. 108–117, 180–209, 255 Mark 5: 23 (Nos. 70, 72, 75–81, 83, 85, 86, 88–98) Mark 6: 119 (Nos. 99–107, 118–179, 210–212, 256, 283–312, 339–352)
Variants	Marks 1 – 6
Specifications
Mass	Mark 1: 3,388 lb (1,537 kg) (without breech) Mark 2: 3,398 lb (1,541 kg) (without breech) Mark 4: 3,160 lb (1,430 kg) (with breech) Mark 5: 3,100 lb (1,400 kg) (with breech) Mark 6: 3,529 lb (1,601 kg) (with breech)
Length	Marks 1–3, 6: 164 in (4.2 m) Marks 4–5: 166.25 in (4.22 m)
Barrel length	Marks 1 and 3: 160 in (4.1 m) bore (40 calibers) Marks 2: 157.5 in (4.00 m) bore (39 calibers) Marks 4–6: 164 in (4.2 m) bore (41 calibers)
Shell	33 lb (15 kg) armor-piercing
Caliber	4 in (102 mm)
Elevation	-15° to +20°
Traverse	−150° to +150°
Rate of fire	8 – 9 round per minute
Muzzle velocity	2,000 ft/s (610 m/s)
Effective firing range	11,500 yd (10,500 m) at 31.2° elevation

The 4″/40 caliber gun (spoken "four-inch-forty-caliber") was used for the secondary batteries on the United States Navy's battleship Iowa, Columbia-class protected cruisers, and the armored cruiser New York, and was the primary batteries on the gunboats Nashville, Wilmington, and Helena.^[1]