3in Gun M5 Anti-Tank

The 3in Gun M5 Anti-Tank was a mediocre design that entered service largely because the head of the US Army Ground Forces considered self-propelled guns to be a waste of money.

Work on the 3in anti-tank gun began in 1940 as part of a wider effort to deal with a general lack of dedicated anti-tank weapons (alongside projects to convert existing 75mm guns to the anti-tank role). It used the Carriage M2 developed for the 105mm howitzer, combined with the 3in gun from the T9 anti-aircraft gun.

The first pilot gun was ready by September 1941 when it underwent trials at the Aberdeen Proving Grounds. These showed that it was significantly better than the 75mm designs, and an order for 100 was placed. However further tests at Fort Bragg revealed a number of minor problems. The biggest problem was that the combat arms didn’t want the new weapon. The Infantry still considered the 37mm gun to be ideal because it was easy to move. The Tank Destroyer branch didn’t want towed guns, preferring self-propelled weapons, which every test had proved to be a vastly superior way of deploying heavy anti-tank weapons, simply because of the speed in which they could be moved into place and deployed for combat. In May 1942 the requirement was cancelled. However it did have some highly placed supporters, most significantly General Lesley McNair, head of Army Ground Forces. He was a former artillery officer who believed self-propelled guns to be a waste of money. McNair was able to overrule General A. D Bruce, head of the Tank Destroyer Centre, and in August 1942 the 3in gun was revived and an order for 1,000 of them was placed. However it had yet to be decided who would actually use the new gun.

McNair continued to push the 3in gun. On 22 August 1942 he ordered the Tank Destroyer Centre to re-examine the issue, commenting that towed guns could use ports that couldn’t cope with heavy tracked vehicles. Bruce responded by pointing out that the towed units needed 300 more men as well as more shipping because they had to find space for both the gun and the heavy prime movers. On 1 January 1943 McNair ordered Bruce to test out a towed battalion, and on 31 March 1943 he ordered the conversion of 15 self propelled battalions into towed battalions. The size issue was dealt with by removing the battalion’s reconnaissance platoon. In November 1943 McNair ordered that half of all tank destroyer units be converted into towed units before the D-Day invasion.

The main problem with McNair’s attitude was that the M5 wasn’t a particularly good anti-tank gun. Both Britain and Germany produced anti-tank guns of a similar size – the 17-pdr and the 75mm PaK 40. The German gun would have satisfied the US Infantry – it was the lightest of the three at 3,142lb, and lowest, at 3ft 11in high (making it not much heavier than the 57mm gun M1 that the US infantry did use). The British gun was heavier and equal in size, but it fired a much more effective anti-tank shell, with 9lb of propellant compared to only 3lb 10oz in the US 3in shell. The 3in shell could penetrate 115mm of armour at 500m, the 17-pdr could penetrate 163mm at the same range.

The heavy gun also needed a powerful prime mover. The M3 half-track was chosen, but proved to be underpowered for the role. On 1 September 1944 the M39 armoured utility vehicle officially replaced it, but that vehicle didn’t enter service in Europe until April 1945, by which time very few towed tank destroyer battalions remained in service.

Production of the 3in gun was on a much smaller scale than of the 37mm (18,702) or 57mm (15,637), with only 2,500 built in 1942-44.

Variants

Carriage M1

The Carriage M1 was the original design, based on the carriage of the 105mm howitzer. It had a flat gun shield.

Carriage M6

The Carriage M6 replaced the flat shield of the M1 with a new sloped gun shield. It was standardized in November 1943 and most existing guns were modified to use the new carriage.

Combat

The 3in anti-tank gun entered combat with the 805th Tank Destroyer Battalion, which reached Italy in October 1943. It saw combat on the Volturno front, at Cassino, and during the fighting at Anzio and around Rome. However the infantry divisions it worked with all would have preferred self propelled guns instead, and in July 1944 the battalion converted to the M18 76mm GMC. In November 1944 a conference of Fifth Army tank destroyer officers held in Florence reported that the 3in gun was ‘grossly inferior to the SP-gun’. However the 3in gun did remained in limited use in Italy, and there was still one towed battalion in service at the end of the war. A total of 58 3in guns were lost. 

By D-Day there were thirty tank destroyer battalions in Britain of which eleven used towed guns. One towed tank destroyer battalion was attached to each infantry division, to provide heavy support for their built in 57mm anti-tank guns.

The towed 3in gun wasn’t a success in Normandy. It was very difficult to move the heavy gun in the bocage country, especially once it had been detached from its prime mover. The gun was too large to easily hide, leaving its crew vulnerable to enemy fire. The gun shield wasn’t suitable cover. Worse, when the Panther started to appear in US sectors the 3in gun proved to lack the armour penetration to deal with it. It could only penetrate the front mantlet armour at ranges of 100-300 yards, dangerously close.

A small number of towed 3in guns took part in the defeat of Operation Luttich, Hitler’s attempt to attack west and cut off US troops that had broken through the western end of the German defensive lines. However the 57mm guns and bazooka teams were seen as more effective, and the self propelled battalions as more useful than either of them. In September General Bradley wanted 40 of the 52 tank destroyer battalions to be self propelled, and only 12 to be towed, and only if they could use the 90mm T5E1 gun.

M10 Gun Motor Carriage near Metz, 1944

The 3in gun was used in the M10 Tank Destroyer (as the modified 3in gun M7, designed for use in vehicles), where it was someone more effective. It still suffered from the poor armour penetration problem, but the mobility of the M10 meant it could get into place far more easily, and out of danger more easily, while the armour gave the crew far better protection than the gun shield. A number of other experimental vehicles also used the M7 or the closely related 3in gun M6.

Several 3in tank destroyer battalions were caught up in the battle of the Bulge. The 820th TD Battalion was in the Loshiem Gap when the Germans attacked and lost 31 of its 36 guns in the early fighting. The 801st TD Battalion took part in the fighting at Krinkelt and lost 15 guns, but did help slow the 12.SS Panzer Division. An analysis of the fighting showed that the 3in gun was of limited value. When fighting alone they lost three guns for each tank destroyed. When integrated into a defensive position they were more effective, but still only had an exchange rate of 1:1.3, not good for a defensive weapon. Loses ran at 35% during December 1944. Self propelled battalions were judged to be five to six times more effective than towed units, with a 1:6 exchange rate when supported by infantry! The First Army lost 119 tank destroyer weapons during the battle, of which 86 were towed guns!

During the rest of the war an effort was made to convert every remaining towed 3in tank destroyer battalion into a self propelled battalion, and by the end of the war only four 3in battalions remained.

The 3in gun was eventually replaced by a 90mm anti-tank gun.

Help - F.A.Q. - Contact Us - Search - Recent - About Us - Privacy