M-5 STUART LIGHT TANK WITH A 57-MM GUNI'm one of those many people who disliked the idea of GI's and allied light tank units fighting the war with the M-3 and M-5 Stuart tank armed with it's piddly 37-mm gun. Yes, I know of the 37-mms good qualities: high velocity and canister shot, etc. And I've read a lot more than some people who discount them as useless when in fact they served well enough. My personal beefs are that the M-24 Chaffee with its 75-mm gun might have been fielded earlier. Heck, the British created armored cars (the AEC) with 6-pounders and 75-mm guns. Why didn't the USA do better?At the very least the M-5 might have been up-gunned with a 57-mm, or so many people have suggested. The idea of using a 57-mm gun sounds obvious - halfway between a 37-mm and 75-mm! - but the reality is something else. The 57-mm M-1 (and its cousin the British 6-pounder) is almost the same weight and size as the USA's 75-mm M-3 cannon. The 57-mm ammunition is almost the same size as the 75-mm M-3's ammunition.If the USA could fit the 57-mm to the M-5, they could have fit the 75-mm into it. They did in fact try mounting the 75-mm M-3 in an M-5 (or properly the turret of an M-8 howitzer motor carriage based on the M-5), and found that the it simply overwhelmed the M-3/M-5 tank chassis.The M-8 Howitzer Motor Carriage was the M-5 hull with an open-topped turret and 75-mm howitzer. It necessitated eliminating the coaxial and bow .30-caliber machine guns (necessary weapons for tanks to fend off close range infantry attacks) and with the open turret it was hardly a tank.Then again, the howitzer with a HEAT round (even the lousy HEAT round available in World War II, able to penetrate 90-mm/3.5-inches of armor) might have done better than a 37. Just a few tweaks and maybe a revised M-5 with a Howitzer might have come to life. But at the time, the USA military probably thought it would have a 75-mm armed light tank ready fairly soon, so why waste the time? They already knew the M-8 would be obsoleted once something better came about like the M-4 tank with a 105-mm howitzer. And so would any tweaked hybrid. Or so they were probably thinking...The only advantage the 57-mm might have given over the 75-mm was lower recoil, which enabled the British to design a 57-mm AT gun weighing 1-1/4 ton as opposed to a 3-inch or 75-mm AT gun that would have weighed up to 2-1/4 to 2-1/2 tons. But the 57-mm had a smaller high explosive shell. Still, later in the war a high velocity APDS shot was developed for the 57-mm giving decent penetration against thicker armor. But no one would have known that while the decision to arm light tanks was being made.Again: a 57-mm was the same size as a 75-mm and it just would not work in the basic M-3/M-5 hull.Mind you: the British armed many of their earlier tanks with the 57-mm because sometimes they were as backwards as the USA was. Early in the war, they focused on anti-armor uses so much that they didn't realize the need for a 75-mm. Thus they used a 57-mm in their tanks, which meant that they carried the same ammo as their 57-mm anti-tank gun units. It wasn't until they received USA M-3 Lee/Grant and M-4 Sherman tanks armed with a 75-mm gun that they discovered they were missing out on a decent HE shell. Which was very useful for countering anti-tank guns, which was one of the main obstacles of the war.Once they experienced the 75, they not only mounted some 75s from some of their damaged Lend Lease US tanks to Churchill tanks, but also developed their own version, firing the same ammunition, for use in their own tanks. What is important is: the British designed their home-grown 75 by using their 6-pounder and increasing the bore size to 75-mm, illustrating how similar the two weapons were. You will note that British tank designs that used the 57-mm usually carried the same number of rounds if they were upgraded to a 75.Mounting the 75-mm gun on a tank in 1941 and 1942 was far-sighted for the USA; but they flummoxed it from there on out.US and allied forces who used the M-3 and M-5 light tank were the victim of plodding development process hindered and interfered with by poor leadership. As early as 1940 it was known that a better light tank than the M-3/M-5 series was needed. The first serious answer was the M-7 light tank - which had some promise - but it was improved until it became a medium tank armed with a 75-mm gun, due to the demands of upper ranks. Which defeated the purpose of its design because the M-4 tank already existed. If they had just focused on creating the M-7 as a 75-mm gun armed light tank, it could have been in production in 1942 in place of the M-5 Stuart.Alas: the M-7 light tank design process failed, and it wasn't until April 1943 that design began on what would become the M-24 Chaffee with a 75-mm gun. A design using ideas from the M-18 Hellcat Gun motor Carriage (tank destroyer) also in development at that time. And as such, delays in development and acceptance meant that while over 4,400 M-24s were produced, few reached Europe in time to enter service with the ground troops before the war ended.So, what the USA needed was not so much an up-gunned M-5 (which was kept in production and service only for a lack of a replacement) but rather technical teams (and leadership) who didn't fritter away years working on esoteric designs only to botch them.Indeed, consider the simplest concept ever: what if the US military had not wasted any time on the M-7 light tank and M-24 Chaffee. What if they had concentrated on the M-18 Hellcat, development of which began in 1942, a year earlier than the M-24. With a .30-caliber coaxial gun and armored roof, and the 76-mm M-1 gun, it would have made a grand light tank. But, the conventional thinking of the time was: it was a tank destroyer and hence not a tank. M-18s did, though, get into use early enough to see fighting late in 1944. Shave off a few months wasted on the M-7 or M-24 and they might have been in service in 1943.Rather than ship so many thousands of M-3s and M-5s overseas, the USA could have been shipping M-18s.And that is why the M-5 Stuart was never armed with a 57-mm gun.NOTE: Do not mistake the M-7 light tank for the 105-mm M-7 Self propelled Howitzer, which was a different machine altogether.