3 - inch Gun M5 3 inch Gun M5 was an anti - tank gun developed in the United States during World War II . The gun combined a barrel of the anti - aircraft gun T9 and elements of the 105 mm howitzer M2 . The M5 was issued exclusively to the US Army tank destroyer battalions starting in 1943 . It saw combat in the Italian Campaign and in the Northwest Europe campaign . While the M5 outperformed earlier anti - tank guns in the US service , its effective employment was hindered by its heavy weight and ammunition - related issues . Losses suffered by towed TD battalions in the Battle of the Bulge and the existence of more mobile , better protected alternatives in the form of self - propelled tank destroyers led to gradual removal of the M5 from front line service in 1945 . Development and production history . In 1940 , the US Army just started to receive its first antitank gun , the 37 mm Gun M3 . While it fitted the request of the Infantry for light , easy to manhandle anti - tank weapon , Artillery and Ordnance foresaw a need for a more powerful gun . This led to a number of expedient designs , such as adaptations of the 75 mm M1897 or towed variants of the 75 mm M3 . Late in 1940 the Ordnance Corps started another project - an anti - tank gun based on the 3 inch anti - aircraft gun T9 . The barrel of the T9 was combined with breech , recoil system and carriage , all adapted from the 105 mm howitzer M2 . The pilot of the weapon , named " 3 inch Gun T10 " , was ready by September 1941 . Although the subsequent testing revealed minor problems , it was clear that the gun , eventually standardized as M5 on carriage M1 , presented major performance improvement over existing designs . Production began in December 1942 . In November 1943 a slightly modified carriage was standardized as M6 . In this carriage a flat shield borrowed from the 105 mm howitzer was replaced by a new sloped one . In January 1944 AGF requested to upgrade the guns built with the early carriage M1 to carriage M6 ; consequently most of the guns that reached the frontline had the M6 carriage . Description . The barrel was adapted from the 3 inch Gun T9 ; it had rifling with uniform right hand twist , with 28 grooves and one turn in 25 inches . Barrel length was 13 . 16 feet . It was combined with breech , recoil system and carriage from the 105 mm Howitzer M2 . The breech was of horizontal sliding type , manual ; the recoil system hydropneumatic . The carriage was of split trail type , equipped with a single equilibrator spring beneath the breech and wheels with pneumatic tires . Organization . Despite the performance advantages , it turned out that no branch of the US Army wanted the new gun . The Infantry considered it too large and heavy . The other possible user , the Tank Destroyer Center , preferred more mobile self - propelled weapons . Finally , pressure from the head of Army Ground Forces , Gen . Lesley McNair , resulted in the gun being adopted by the TD Center . McNair ' s opinion was apparently influenced by the experience of the North African Campaign , where self - propelled guns were found to be hard to conceal . On 31 March 1943 AGF ordered to convert fifteen self - propelled tank destroyer battalions to a towed form ; eventually AGF decided that half of TD battalions should be towed . A towed TD battalion possessed 36 pieces , in three companies of 12 . M3 Halftrack s were issued as prime movers . The organization from 1 September 1944 authorized M39 Armored Utility Vehicle instead , but these only reached frontline in spring 1945 . Those towed tank destroyer battalions were attached to US Army division to improve their anti - tank capabilities . Most often , a complete battalion was attached to an infantry division . In some cases towed TD battalions were attached to armored or airborne divisions ; sometimes companies of the same battalion were given to different divisions ; and sometimes a single division had several TD battalions - including a mix between towed and self - propelled - at once . Combat service . In October 1943 the first towed battalion - the 805th TD - arrived in Italy . Subsequently the M5 saw combat in the Italian Campaign and in the Northwest Europe . One of the most notable engagements came during the German counterattack on Mortain in August 1944 . The 823rd TD , attached to the 30th Infantry Division , played a key role in the successful defence of Saint Barthelemy , destroying fourteen tanks and a number of other vehicles , though at the price of losing eleven of its guns . In addition to the anti - tank role , the gun was often used to supplement divisional field artillery or to provide direct fire against enemy fortifications ( e . g . a combat report from the 614th TD mentioned a two - gun section firing 143 shells at an enemy post , achieving 139 hits ) Although the M5 easily outperformed older anti - tank guns in the US service , it was large and heavy - making it hard to manhandle into position - and its anti - armor characteristics were found to be somewhat disappointing . In part that reputation reflected initial problems with fuses of APCBC / HE shells . The 3 inch APHE round which was based on the naval 3 inch round , had a small charge in the rear of the round which was supposed to explode after penetration of the targeted tank ' s armor plating . Unfortunately it was discovered that it exploded on impact or shortly after causing the round not to penetrate . It is still a puzzling mystery as to why this problem was never addressed with a better base fuze or even removing the small HE charge in the rear of the round . This was also the problem with the M10 tank destroyer . APDS round was never developed for the M5 ; an APCR round existed ( see ammunition table below ) , but it is not clear if it was ever issued to towed TD battalions . As a result of the aforementioned shortcomings , commanders and troops generally preferred an alternative in form of self - propelled tank destroyers , which offered better mobility and also better protection for their crews . The greatest test of the TD battalions and their M5 guns came during the Battle of the Bulge . In this battle , towed tank destroyers fought much less successfully and suffered much higher losses than the self - propelled ones . A report from the aforementioned 823rd battalion said that " tank destroyer guns were one by one flanked by enemy tanks and personnel driven from guns by small arms and machine guns fire " . Taking the recent combat experience into account , on 11 January 1945 the War Department confirmed a request to convert the towed TD battalions to the self - propelled form . This decision meant gradual removal of the M5 from frontline service , a process that continued until the end of the war in Europe . Today , the M5 is utilized by the US Army for . The Presidential Salute Guns Platoon of The Old Guard currently maintains a battery of ten M5 ' s at Fort Myer for service mainly in the National Capital Region . Ammunition . The M5 utilized fixed ammunition , with the same 76 . 2x585R cartridge case - designated " 3 inch Cartridge Case Mk IIM2 " - as other descendants of the " 3 inch M1918 " anti - aircraft gun , and had basically the same barrel . That meant the same anti - tank characteristics as those of vehicle mounted anti - tank guns derived from the T9 , namely the M6 ( used in the " 3 inch Gun Motor Carriage M5 " , which never reached production ) and the M7 ( which was the main armament of the 3 inch Gun Motor Carriage M10 and the M6 Heavy Tank ) . The below table lists ammunition available for the three guns . It is possible that some types ( e . g . the APCR round ) were never issued to towed TD battalions .