The Mark 1 was a simply constructed weapon used as a boat gun. Monobloc construction with a Fletcher breech mechanism and used a hydraulic recoil piston screwed directly onto the gun.
The Mark 1 Mod 1 was of similar construction but used a solid lug for the piston rod. The barrel slid in the cradle and had two keys on the horizontal line through its center. Used a modified Fletcher breech mechanism.
| Designation | 3"/21 (7.62 cm) Mark 1 |
|---|---|
| Ship Class Used On | N/A |
| Date Of Design | About 1890 |
| Date In Service | About 1890 |
| Gun Weight | 384 lbs. (174 kg) |
| Gun Length | 69.6 in (1.768 m) |
| Bore Length | 64.3 in (1.633 m) |
| Rifling Length | N/A |
| Grooves | N/A |
| Lands | N/A |
| Twist | RH 1 in 29.89 |
| Chamber Volume | N/A |
| Rate Of Fire | about 8 - 9 rounds per minute |
| Type | Bag |
|---|---|
| Projectile Types and Weights | HE: 13 lbs. (5.9 kg) |
| Bursting Charge | N/A |
| Projectile Length | N/A |
| Propellant Charge | N/A |
| Muzzle Velocity | 1,150 fps (351 mps) |
| Working Pressure | 9.5 tons/in2 (1,500 kg/cm2) |
| Approximate Barrel Life | N/A |
"US Naval Weapons" by Norman Friedman
"A Treatise on Rifling of Guns" by Carl F. Jeansén
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"United States Naval Guns: Their Marks and Modifications"
Ordnance Pamphlet No. 127, December 1916, Second Revision June 1924
Gene Slover's Navy Pages
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Special help from Leo Fischer
03 December 2006 - Benchmark
07 August 2017 - Converted to HTML 5 format