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Object Title

Gun and carriage - 7-inch gun of 72 cwt, Rifled Breech Loading on a Garrison, Carriage, Sliding, Medium No.15 on a Platform, Traversing, Medium No.14

Gun and carriage - 7-inch gun of 72 cwt, Rifled Breech Loading on a Garrison, Carriage, Sliding, Medium No.15 on a Platform, Traversing, Medium No.14

Date

1862

Object Number

XIX.506

Provenance

Retrieved from a car park in Ireland where it was being used as a bollard and around which excavation had occurred.

Physical Description

The barrel was constructed with an A-tube or inner barrel made of coils joined together lengthways and are of solid forging, that is, solid cylinders of wrought iron and then bored out. The breech-piece and trunnion ring are forged and together with four coils, the breech piece, B tube and trunnion ring are built up by shrinking these parts over the A tube. Following this process the barrel is brought to the proper size and shape by turning, boring etc., and the piece so completed, all but the rifling and the preparation of the gun for breech fittings. The large assemblage at the breech - essentially two spheres with handles - comprises the Armstrong "screw" breech mechanism. This unique method of breech loading used a heavy block called a vent-piece - a block of iron or steel that closes the end of the bore after loading - placed in a vertical slot in the barrel behind the chamber once the projectile and bag charge have been loaded. This was then manually screwed tight against the vent-piece. Obturation or gas sealing was provided by a metal cup on the front of the vent-piece. To fire, a vent tube was inserted into the top of the vent-piece and initiated. The rifling grooves were carriaed right through from end to end by means of a cutter fixed to a metal head secured to a twisted bar. The bar, square in section, passes through a fixed nut, so that as the head and cutting tool worked up and down the bore the grooves were cut with a certain amount of twist depending on the twist given to the bar, in this gun 1 turn in 37 calibres. Only one groove is cut at a time and since there are many the rifling is known as polygroove. Some idea of the precise nature required for this rifling can be provided by considering the depth of the rifling between the grooves was 1.5 mm (0.06 in) and the distance between the grooves known as the land was 4.2 mm (0.166 in). The wooden assemblage for Haxo deployment comprises a sliding carriage and platform.

Techniques

Built-up construction

Materials

Dimensions

BarrelBore177.8 mm
BarrelLength2527 mm
BarrelLength2997 mm
ChaseLength1153 mm
First ReinforceLength240 mm
TrunnionsLength265 mm
Second ReinforceLength525 mm
BreechLength814 mm

Firearms/Artillery

Serial Number RGF56B

Calibre

177.8 mm

Inscriptions and Marks

Inscription
RGF No.56 B 1862
Left trunnion
Inscribed
Royal cipher
Victoria
First reinforce
In relief

Associations

Places Britain

Notes

Although this gun is the 72 cwt version of two variants, it was the 82 cwt that was intended for this gun position at Fort Nelson. Obviously the latter was a larger, heavier gun, barrel length only differed by 2 inches, but internally, six coils were used instead of four in the 72 cwt. This family of guns was recommended in 1859 as a 100-pounder, for the navy, as a broadside or pivot gun toreplace the 68-pounder smooth-bore. It was soon discovered though that owing to the gun's lightness, its on board ship recoil was excessive hence only 76 of this weight were manufactured. In 1863 its designation was changed to "light" 110-pounder and then finally to the 7-inch of 72 cwt. It is used only for Garrison service whereas the 82 cwt was uswed for both land and sea service. The projectiles were either the common or segment shell or shot. The full charge was 10 lb of Rifled Large Grain powder. Breech loading fell from favour in 1864 following faults and accidents resulting in the manufacture of no new breech loading guns and between this date much experimentation and committee deliberation with the conclusion in 1870 that breech loading guns were to be discontinued in favour of muzzle loading. The maximum range was 3200 m (3,500 yd).In 1854, William Armstrong (1810-1900), later Lord Armstrong, submitted a proposal for a rifled field piece of revolutional design to the Duke of Wellington. He requested that he might also be permitted to manufacture it himself if it proved acceptable. After two years the gun was ready for trial and after a long series of these six different natures were adopted into British service in 1859. These were the 6-pounder, 9-pounder, 12-pounder, 20-pounder and 40-pounder as well as the 7-inch gun. The carriage and platform were constructed in the Hampsire County Museum Service's workshops at Chiklcomb House, Winchester.The Palmerston Forts Society have for many years conducted public firing and drill demonstrations on this gun, carriage and platform.

Image of Gun and carriage - 7-inch gun of 72 cwt, Rifled Breech Loading on a Garrison, Carriage, Sliding, Medium No.15 on a Platform, Traversing, Medium No.14 Also known as the 'Armstrong gun' and the'Light 110-pounder'.
The barrel comprises a series of tubes and coils shrunk on an inner rifled tube.
Image of Gun and carriage - 7-inch gun of 72 cwt, Rifled Breech Loading on a Garrison, Carriage, Sliding, Medium No.15 on a Platform, Traversing, Medium No.14 Also known as the 'Armstrong gun' and the'Light 110-pounder'.
The barrel comprises a series of tubes and coils shrunk on an inner rifled tube.
Image of Gun and carriage - 7-inch gun of 72 cwt, Rifled Breech Loading on a Garrison, Carriage, Sliding, Medium No.15 on a Platform, Traversing, Medium No.14 Also known as the 'Armstrong gun' and the'Light 110-pounder'.
The barrel comprises a series of tubes and coils shrunk on an inner rifled tube.
Image of Gun and carriage - 7-inch gun of 72 cwt, Rifled Breech Loading on a Garrison, Carriage, Sliding, Medium No.15 on a Platform, Traversing, Medium No.14 Also known as the 'Armstrong gun' and the'Light 110-pounder'.
The barrel comprises a series of tubes and coils shrunk on an inner rifled tube.