75 mm gun M2–M6

They were primarily mounted on tanks, such as the M3 Lee and M4 Sherman, but one variant was also used as an air-to-ground gun on the B-25 Mitchell medium bomber aircraft.

They believed that the American observers working with the British before Dunkirk had appreciated the effectiveness of such a dual purpose weapon, and so it was made a prime requirement for US tank production.

The field gun origins of the ordnance and ammunition ensured that the M2/3/6 series HE round was highly effective for its caliber.

Other rounds fired by the 75 mm tank guns included the T30 canister shot for use against troops in the open at short range.

This, which was essentially a giant shotgun shell full of large numbers of steel balls, was used primarily in the Pacific.

The blunt armor-piercing cap, made of a softer metal, helped to prevent shell shatter at higher velocities and against sloped and face-hardened armor.

The M61 had a muzzle velocity of 617 m/s (2024.28 ft/s) and was credited with the ability to penetrate 81 millimetres (3.2 in) of rolled homogeneous armor plate at 0° from vertical at 500 yards range, which was a quite acceptable performance by the standards of 1942.

This was somewhat compensated by the M4 Sherman's improved armor over the earlier M3 Lee making up for the 75mm M3's diminishing battlefield dominance; the German weapons testing agency Wa Pruef 1 estimated that the M4's standard 56º-angled glacis was impenetrable to the KwK 40 when standing at a 30-degree side angle, while the 75 mm M3 could penetrate the Ausf G's hull from 100 m in the same situation.

The US Army also experimented with mounting the M3 on various wheeled carriages for use as anti-tank gun, but the program was cancelled due to a lack of requirement.

A lightweight version of the M3 with a lighter thin-walled barrel and a different recoil mechanism of the concentric hydrospring type (similar to the modern M256 smoothbore gun) that was used in the Douglas A-26 Invader and the North American B-25H Mitchell bombers.