Andy Naude
Well-Known Member
My "find" of the day, thank you George. 3 inch 70 calibre drill. This round saw limited use. It was designed in 1945, produced in 1957 and used in 1958 by the U S Navy on eight of the U S Ships. It also saw limited use on a few British ships.
Is this Drill round of US Manufacture or of British or a bit of both ?
These guns had their genesis in the Kamikaze attacks of World War II. A larger-caliber projectile was needed to replace the 20 mm Oerlikon and 40 mm Bofors automatic weapons as they had proven to be too small to kill-stop suicide planes. This need led to the accelerated development of 3" / 50 cal (76.2 mm) guns equipped with autoloaders and later to the 3"/70 (7.62 cm) project. The 3" (7.62 cm) caliber was selected for these weapons as it represented the smallest-size projectile that could still be fitted with a VT (radar proximity) fuze. BuOrd considered the 3"/70 (7.62 cm) twin mounting to be superior to the single 5"/24 Mark 425"/54 (12.7 cm) for defending against fast aircraft and guided missiles.
The development of the ammunition and water-cooled barrel was a joint British-American project, but each navy designed a completely different gun mounting, with the British one being the 3"/70 (7.62 cm) Mark VI..
/38
This twin mount was intended to replace the older 5" /38 (12.7 cm Mark 12mounts on a one-for-one basis and to become the standard weapon for post-war destroyers. However, its complex nature resulted in a long development cycle and by the time it was ready for service use in 1956 the usefulness of antiaircraft shellfire was limited. In addition, the mounting proved to be so unreliable and hard to maintain that it was quickly withdrawn from duty and may have had the shortest service life of any weapon system ever used by the US Navy. It has been said that the only advantage of this mounting was that the gun shield let you work on them out of the weather. Most mounts were replaced within a few years with other weapons and the only US warship to retain the 3"/70 (7.62 cm) to the end of her career was USS Norfolk (DL-1).
As per the nomenclature change in the US Navy after World War II, the Mark 37 designation was for the mounting, not the gun itself. The gun went through four major revisions. The Mark 23 was a prototype used to test the operation of fully-automatic firing. The Mark 24 was similar but slightly lighter. The Mark 25 used a rapid-fire horizontal-wedge breech. The Mark 26 was the service version and was a water cooled monobloc type with a horizontally sliding breech mechanism. The barrel on this last Mark had a three caliber smoothbore section near the muzzle (Probertised) to reduce loss of velocity and to act as a flash suppresser. The breechblock opened mechanically as the gun recoiled and closed automatically as soon as the next round was loaded. The barrel is attached to the breech ring by interrupted threads (bayonet joint) and can be removed without dismounting the gun.
Is this Drill round of US Manufacture or of British or a bit of both ?
These guns had their genesis in the Kamikaze attacks of World War II. A larger-caliber projectile was needed to replace the 20 mm Oerlikon and 40 mm Bofors automatic weapons as they had proven to be too small to kill-stop suicide planes. This need led to the accelerated development of 3" / 50 cal (76.2 mm) guns equipped with autoloaders and later to the 3"/70 (7.62 cm) project. The 3" (7.62 cm) caliber was selected for these weapons as it represented the smallest-size projectile that could still be fitted with a VT (radar proximity) fuze. BuOrd considered the 3"/70 (7.62 cm) twin mounting to be superior to the single 5"/24 Mark 425"/54 (12.7 cm) for defending against fast aircraft and guided missiles.
The development of the ammunition and water-cooled barrel was a joint British-American project, but each navy designed a completely different gun mounting, with the British one being the 3"/70 (7.62 cm) Mark VI..
/38
This twin mount was intended to replace the older 5" /38 (12.7 cm Mark 12mounts on a one-for-one basis and to become the standard weapon for post-war destroyers. However, its complex nature resulted in a long development cycle and by the time it was ready for service use in 1956 the usefulness of antiaircraft shellfire was limited. In addition, the mounting proved to be so unreliable and hard to maintain that it was quickly withdrawn from duty and may have had the shortest service life of any weapon system ever used by the US Navy. It has been said that the only advantage of this mounting was that the gun shield let you work on them out of the weather. Most mounts were replaced within a few years with other weapons and the only US warship to retain the 3"/70 (7.62 cm) to the end of her career was USS Norfolk (DL-1).
As per the nomenclature change in the US Navy after World War II, the Mark 37 designation was for the mounting, not the gun itself. The gun went through four major revisions. The Mark 23 was a prototype used to test the operation of fully-automatic firing. The Mark 24 was similar but slightly lighter. The Mark 25 used a rapid-fire horizontal-wedge breech. The Mark 26 was the service version and was a water cooled monobloc type with a horizontally sliding breech mechanism. The barrel on this last Mark had a three caliber smoothbore section near the muzzle (Probertised) to reduce loss of velocity and to act as a flash suppresser. The breechblock opened mechanically as the gun recoiled and closed automatically as soon as the next round was loaded. The barrel is attached to the breech ring by interrupted threads (bayonet joint) and can be removed without dismounting the gun.
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