4 . 5 - inch Gun M1 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 Model 1906 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 . 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 . The production started in September 1942 and continued until February 1944 . 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 . 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 . Service . The M1 equipped 16 or 17 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 . 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 . Variants . 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 . Ammunition . The M1 utilized separate loading , bagged charge ammunition . Only high explosive projectile was available . 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 . The velocity and range data in the table below is for the M8 charge .