4.5-inch Gun M1

4.5 inch Gun M1 on Carriage M1
4.5 inch Gun M1 at the U.S. Army Field Artillery Museum, Ft. Sill, Oklahoma
Type	Field gun
Place of origin	United States
Service history
In service	1942–1945
Used by	United States
Wars	WWII
Production history
Designed	1939–1941
Produced	1942–1944
No. built	416
Specifications
Weight	5,654 kg (12,465 lbs)
Length	8.15 m (27 ft)
Barrel length	Bore: 4.756 m (15 ft 7 in) L/41.6 Overall: 4.918 m (16 ft 2 in) L/43
Width	2.4 m (7 ft 10 in)
Height	2.12 m (6 ft 11 in)

Shell	separate-loading bagged charge
Caliber	114 mm / 4.5 inch
Breech	interrupted screw
Recoil	hydropneumatic
Carriage	split trail
Elevation	0° to +65°
Traverse	53°
Rate of fire	Burst: 4 rounds per minute Sustained: 1 round per minute
Muzzle velocity	693 m/s (2,274 ft/s)
Maximum firing range	19,317 m (21,125 yds)
Sights	panoramic, M12

The 4.5 inch Gun M1 was a field gun developed in the United States in the beginning of World War II. It shared the same carriage with the 155mm Howitzer M1 and fired the same ammunition as the British BL 4.5 inch Medium Field Gun. The weapon was used by the US Army in Northwest Europe late in the war for corps support; with the end of hostilities it was declared obsolete.

Development and production

In 1920 the US Army Ordnance started to work on a new medium field gun. Since the US Army had already employed the 4.7 inch Gun M1906 during World War I, this caliber was also selected for the new weapon. The development resulted in 4.7 inch Gun M1922E on Carriage M1921E. Due to lack of funding, the design never reached production.^[1]^[2]

In 1939 the program was restarted; the renewed design, designated 4.7 inch Gun T3, was ready by early 1940; it utilized the same carriage as the concurrently developed 155 mm howitzer. At this stage, the army decided to change the weapon to use the British 4.5 inch ammunition. The modified gun was standardized in April 1941 as 4.5 inch Gun M1 on Carriage M1.^[1]^[2]

The production started in September 1942 and continued until February 1944.^[2]

Production of M1^[3]
Year	1942	1943	1944	Total
Produced, pcs.	41	345	40	416

Description

The M1 was very similar in construction and appearance to the 155mm Howitzer M1. The only significant difference was its tube of 4.5 inch (114 mm) caliber. The tube had uniform right hand twist, with one turn in 32 calibers.^[4] The unbalanced weight of the barrel was supported by two equilibrator springs. The breach was of interrupted screw type; the recoil system hydropneumatic, variable length. The carriage was of split trail type, unsprung and had wheels with pneumatic tires. In firing position, the weapon was supported by a retractable pedestal. The gun was equipped with M12 panoramic sight.^[5]

Service

155 mm Howitzer M1 (left) and 4.5 inch Gun M1 (right) at the U.S. Army Field Artillery Museum, Ft. Sill, OK. Note the similarity between the two pieces.

The M1 equipped 16^[2] or 17^[6] field artillery battalions in the Northwest Europe, where it was employed for corps support. M5 High Speed Tractor was assigned as prime mover. The weapon was declared obsolete in September 1945.^[1]^[2]

The gun had good range, nearly five km longer than its 155 mm howitzer sibling and longer than the 155 mm Gun M1918MI. It was out-ranged by another 155 mm gun, the Long Tom, but the latter was nearly three times heavier.

On the other side, the 4.5 inch gun was criticized for insufficient power of its high-explosive shell. The shell was produced from low grade ("19 ton") steel, which necessitated thick walls. As a result, it carried only about two kg of TNT or substitute, in fact less than the 105 mm high-explosive shell. Additionally, it was felt that having a small number of guns of atypical caliber unnecessarily complicated logistics.^[1]^[2]

Variants

External image
4.5 inch GMC T16.

4.7 inch Gun M1920 on Carriage M1920.^[2]
4.7 inch Gun M1922E on Carriage M1921E.^[2]
4.7 inch Gun T3 (1940).^[2]
4.5 inch Gun M1 on Carriage M1 (1941).^[1]

The weapon was experimentally mounted on a lengthened chassis of the M5 light tank, in mount M1. The resulting vehicle received the designation 4.5in Gun Motor Carriage T16. A single prototype was built.^[7]

Ammunition

The M1 utilized separate loading, bagged charge ammunition. Only high explosive projectile was available.^[8]

The projectile could be fired with propelling charge M7 (normal) at reduced velocity or with propelling charge M8 (super) to achieve full velocity. The dummy propelling charge M6 simulated the M8 charge.^[9] The velocity and range data in the table below is for the M8 charge.

Available ammunition.^[4]^[8]^[10]
Type	Model	Projectile weight, kg	Filler	Muzzle velocity, m/s	Range, m
HE	HE M65 Shell	24.9	TNT, 2.04 kg or Amatol 50/50, 1.85 kg or Trimonite, 2.10 kg	693	19,317
Dummy	Dummy M8 Projectile			-	-

Propelling charges^[9]
Model	Weight, complete, kg	Components
M7 (normal)	2.95	Single section
M8 (super)	5.08	Base charge and increment
M6 (dummy)	5.40	Base charge and increment

Concrete penetration, mm^[4]
Ammunition \ Distance, m	0	914	4,572	9,144
HE M65 Shell (meet angle 0°)	1,158	1,067	640	366
Different methods of measurement were used in different countries / periods. Therefore, direct comparison is often impossible.

Notes

1 2 3 4 5 Hogg - Allied Artillery of World War II, p 50-51.
1 2 3 4 5 6 7 8 9 Zaloga - US Field Artillery of World War II, p 18-19.
↑ Zaloga - US Field Artillery of World War II, p 9.
1 2 3 Hunnicutt - Stuart: A History of the American Light Tank, p 506.
↑ Technical Manual TM 9-2005 volume 3, Infantry and Cavalry Accompanying Weapons, p 59-62.
↑ Anderson - US Army in World War II.
↑ Hunnicutt - Stuart: A History of the American Light Tank, p 337-338.
1 2 Technical Manual TM 9-1904, Ammunition Inspection Guide, p 486-490.
1 2 Technical Manual TM 9-1901, Artillery Ammunition, p 300-304.
↑ Technical Manual TM 9-1901, Artillery Ammunition, p 183-184.

References

Wikimedia Commons has media related to 4.5 inch Gun M1.

Hogg, Ian V. (1998). Allied Artillery of World War Two. Crowood Press, Ramsbury. ISBN 1-86126-165-9.
Hunnicutt, R. P. (1992). Stuart: A History of the American Light Tank. Presidio Press. ISBN 0-89141-462-2.
Williford, Glen M (2016). American Breechloading Mobile Artillery 1875-1953. Thomas D. Batha. Schiffer Publishing Ltd. ISBN 978-0-7643-5049-8.
Zaloga, Steven J. (2007). US Field Artillery of World War II. New Vanguard 131. illustrated by Brian Delf. Osprey Publishing. ISBN 978-1-84603-061-1.
Technical Manual TM 9-1901, Artillery Ammunition. War Department, 1944.
Technical Manual TM 9-1904, Ammunition Inspection Guide. War Department, 1944.
Technical Manual TM 9-2005 volume 3, Infantry and Cavalry Accompanying Weapons. War Department, 1942.
Technical Manual TM 9-328 4.5-inch Gun M1 and 4.5-inch Gun Carriage M1. War Department. December 1943.
"Anderson, Rich - US Army in World War II at MilitaryHistoryOnline website". Archived from the original on 14 December 2007. Retrieved 2007-11-20.

United States artillery of World War II
Tank guns	37 mm gun M5/M6 75 mm gun M2/M3/M6 76 mm gun M1 3 inch gun M7 90 mm gun M3 105 mm howitzer M4
Anti-tank guns	37 mm M3 57 mm M1 75 mm M1897 3 inch M5 90 mm T8 105mm T8
Field, medium and heavy guns	75 mm M1897 75 mm howitzer M1 105 mm howitzer M2 105 mm howitzer M3 4.5 inch gun M1 155 mm howitzer M1918 155 mm howitzer M1 155 mm gun M1918MI 155 mm gun M1/M2 "Long Tom" 8 inch howitzer M1/M2 8-inch gun M1 240 mm howitzer M1
Mortars	60 mm mortar M2 81 mm mortar M1 4.2 inch mortar M2 Little David
Other vehicle-mounted	75 mm howitzer M2/M3 75 mm gun M1897 105 mm howitzer M2 155 mm gun M1918MI 155 mm gun M2
Anti-aircraft guns	37 mm M1 40 mm M1 3-inch gun M1917 3 inch M3 90 mm M1 120 mm M1
Coast artillery guns	3-inch gun M1903 90 mm M1 6-inch gun M1903 155 mm gun M1918MI 8-inch Mk. VI 8-inch gun M1888 10-inch gun M1895 12-inch coast defense mortar 12-inch gun M1895 14-inch gun M1907 16-inch gun M1895 16-inch gun M1919 16-inch Marks 2 and 3 16-inch howitzer M1920
Railway artillery	8-inch Mk. VI 8-inch M1888 12-inch coast defense mortar 14-inch M1920

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