Since British and French tanks made their presence along the West Front during World War 1 (1914-1918), it fell to the Germans on the other side of the battlefield to develop counters which ultimately evolved along several avenues - a tank of their own in the forgettable A7V and the Mauser 1918 T-Gewehr anti-tank rifle being two notable developments. Chiefly, it was artillery that remained a tank's worst enemy in the war accounting for more of their destruction than any other weapon (although general mechanical breakdowns also proved an early tank's undoing).
During the interwar years following, engineers set about on utilizing the basic concept of the field gun as a towed anti-tank weapon. These evolved into 37mm and 50mm caliber forms until tank development progressed beyond the effectiveness of these weapon systems. By the time of World War 2, the 37mm type was becoming limited and the 50mm type was soon to reach its battlefield usefulness. This pushed development of larger-caliber anti-tank guns which came in the 76mm caliber range.
The United States Army had begun development of such a weapon as early as 1940 and took the gun component of the T9 anti-aircraft system and mated it to the carriage of the M2 field howitzer. The weapon included the breech and recoil mechanism of the howitzer design for expediency. In September of 1941, the weapon emerged as the prototype "3-inch Gun T10" and it entered the requisite testing phase which proved the overall arrangement sound. This then led to the gun's adoption as the "3-inch Gun M5" in U.S. Army service. Production was quickly enacted in 1942 to which field units - the American Army already committed to World War 2 by now - reached frontlines in 1943. Production the first year totaled 250 units followed by 1,250 units in 1943. 1944 saw 1,000 additional guns added and total manufacture reached approximately 2,500 weapons by the end of the war in September of 1945 (production had ended back in 1944).
As completed, the M5 utilized a conventional artillery piece arrangement. There were two, rubber-tired road wheels with metal rims and a split trail carriage system for towing the system. The gun component included the over-under recoil mechanism (hydropneumatic) and reloading was through the breech end of the system, the breech being a horizontal block type arrangement. The barrel lacked any sort of muzzle brake and projectiles were of 76.2x585mmR caliber. The carriage system included a flat gun shield with early production models until a November 1943 shift saw a sloped shield added, producing the M6 carriage standard. All previous guns were then standardized to the M6 carriage in a January 1944 initiative. The gun mounting hardware allowed for an inherent elevation span of -5 to +30 degrees and traverse was possible up to 45-degrees to either side. The complete system's combat weight was 4,875lbs.
A well-trained and reasonably seasoned gunnery crew could unleash twelve rounds per minute. Muzzle velocity was rated at 2,600 feet per second for each outgoing shell. Maximum range reached over 10,000 yards though actual engagement ranges were much more constrained for increased accuracy. As the weapon was a gun and not a howitzer, it required line-of-sight on the target (i.e. no plunging fire). Additionally, its carriage design required a mover vehicle to tow it into action - typically an M3 Half-Track mover - the gunnery crew could then make finer adjustments once the weapon was dropped off.
In practice, U.S. Army forces were not fond of their new weapon for it proved too heavy to be of real tactical use along the mobile fronts of World War 2. The Tank Destroyer Center was forced to adopt the series and replace a portion of their self-propelled tank destroyer units with the towed gun. First combat use was during the Italian Campaign with forces of the 805th TD group and, from then on, the weapon did prove its worth as a tank-killing system though there arose problems with the ammunition type in play (APHE, based on the 3" naval shell), particularly in the fuses being used - detonating on impact and not delayed. Additionally, commanders favored the protection and mobility found in self-propelled tank destroyer types and the true value of the M5 series was never wholly realized. Those M5 guns present at the famous Battle of the Bulge fared poorly when compared to self-propelled versions which further damaged the case for the gun's long-term existence.
To that end, the M5 began to see a more reduced role towards the close of fighting in Europe and, ultimately, the end of the whole war in September of 1945. The weapon, therefore, went on to lead a rather short service life. Some units managed a post-war existence in ceremonial service and continue to this day through the Presidential Salute Guns Platoon from Fort Myer.