Why Did The RAF Use .303 Caliber Machine Guns in WW2? The Surprising Answer

One question that comes up a lot is why did the British persist with arming their aircraft with .303 machine guns for much of the Second World War? Shirks, those lambies are just dumb. Yeah, the Englanders in dumb. Well, as strong an argument as that is, perhaps there's more to it. The usual arguments boil down to the following. British officials were just incompetent. It was cheaper to use a surplus of World War I ammunition. The .303 was just the best gun available to the British at the time. So which of these are actually true? Well, here's what I found out. And the answer is actually much more surprising than I originally thought. So let's begin by setting the scene. During the First World War, British aircraft had been equipped largely with either the Vickers machine gun or the American designed Lewis machine gun. These were both armed with .303 caliber rounds and were adapted models of the same guns used by the infantry. By 1918, the standard armament for British fighters was two machine guns, either twin Vickers or one paired with the Lewis gun, as in the case of the SE5A. Against enemy aircraft of the day, they were highly effective. And as the 1920s came and went, not a lot changed in British fighter armament. Bomber armament during the First World War usually consisted of a single or twin Lewis guns mounted on a rotating scarf ring for an observer, as with the Bristol fighter, or multiple Lewis guns in the case of the Hanley page type series. Two seater aircraft also often had a fixed forward firing machine gun. With the advent of faster aircraft in the early 1930s, many of which were now constructed largely for metal, a need for heavier armament was reconsidered. The question was, could a .303 still damage an aircraft enough to shoot it out of the sky? As the veteran Vickers and Lewis machine guns were bulky and heavy, the British were looking for a replacement aerial machine gun for their aircraft. During trials and tests throughout the 1920s and into the 1930s, the Air Ministry evaluated their current .303 calibre armament against other larger rounds. The Air Ministry tested a scaled up version of the Vickers gun, now a .50 calibre machine gun, against the American Browning .50 calibre, which was both heavier and more powerful. At the time it was found that the .50 cal certainly created a larger hole than the .303, but when the machine guns were compared in terms of weight, the future Browning .303 was the victor. It's actually a good thing, perhaps, that the .50 cal was rejected as ultimately the British would have adopted the Vickers version, which would serve with the Army and Navy, and prove to pack less of a punch than the American gun. As a side note, reportedly, both Italy and Japan developed a version of the Vickers .50 calibre machine gun, which, with its lower effectiveness, may have ultimately saved Allied lives. Tests were also made with the Swiss Oerlikon 20mm cannon, developed from the German Beck machine gun used in the Great War. When comparing the .303 calibre round to the 20mm, there was no contest. The bigger and heavier explosive shell could inflict much more damage than the rifle calibre round. However, it was deemed that no suitable 20mm gun was available that could match the .303 machine gun for reliability and rate of fire. A pin was put in this 20mm option until it became absolutely essential to use them in all aircraft. By the time the most famous WWII British fighters and bombers were coming off the drawing boards, the Air Ministry had selected the armament that would be fitted to most British aircraft during the approaching conflict. Selected were the .303 American design Browning machine gun and the .303 Vickers gas operated machine gun, known as the VGO or Class K. The former was heavily modified from the original American design to turn it from a closed to an open bolt system, as well as converting it to a .303 calibre round. The gun was modified to allow for the heating issues caused by using cordite and to reduce it jamming and its damage to the gun. Ultimately, what dictated the choice of armament for the British and all nations was a combination of factors, namely weight, rate of fire, relative destructiveness and availability, to name but a few. The Browning .303 boasted roughly a 1,200 rounds a minute rate of fire and the VGO could fire up to 950 rounds a minute. That's compared to the Browning .50 calibre AN M2 which then fired around 800 rounds per minute and the Hispano HS404 which could get up to 850 rounds per minute. Of course, it needs to be noted here that the .50 cal trialled by the British in the 1930s was not the same model being used by 1943 in American fighters. If it had been, perhaps this would be a different conversation. Nevertheless, at the time it had a much lower rate of fire than the .303. This higher rate of fire was taken into consideration when, in 1934, the Air Ministry took advice from the Operational Requirements Branch. It said that the next generation of fighter aircraft should be fitted with a battery of six, but ideally eight, machine guns in order to hit faster moving enemy aircraft. This is a story which involves a very unlikely contributor and if you want to find out more, please watch my video about Hazel Hill. It's a great story. If you're enjoying this video so far and you want to support my channel, then please just like the video to help it spread to more people. I really appreciate that. In terms of weight, which is a huge factor in the performance of an aircraft, the .303 Browning was the leanest machine gun at around 10 kilograms, the .50 Browning weighed 29 kilograms, and the Hispano about 50 kilograms. Of course you need ammunition for a machine gun to be effective, so weight also determines how much you could carry to the fight. A .303 round weighed roughly 24 grams, a .50 Cal was around 112 grams, and a 20mm Hispano cannon used a 257 gram shell. These rough numbers show you just how much bigger the other two rounds were compared to the .303. In addition to this, you had to calculate for the links, ammo boxes, mounts and other armament paraphernalia. In short, with a .303 Browning machine gun, you could carry almost 3 for every .50 Cal and up to 5 for every Hispano. You could also carry more ammunition. Of course, this would change later in the war when more powerful aircraft were available. So perhaps logic said in the mid-1930s, more was better than less. This might also be because the Air Ministry had little faith in their pilots' gunnery skills. Having more rounds gave you a better chance of actually hitting something. This notion seems applicable with the level of training Battle of Britain era pilots received and the pre-war tactics used. This lack of gunnery prowess certainly wouldn't be the case by 1942 or 1943. It's often said that the British kept the .303 caliber machine gun because it was the same round used by its infantry. While it's true that the ball round used in a Spitfire or Blenheim was essentially a normal rifle bullet, the tracer and incendiary rounds were specially made for the task. While they may have had leftover ammunition from the Great War, I feel that perhaps it was the cost of reconfiguring the armament industry that may have been a bigger factor. Uniformity is much more efficient and cost effective, and in this, the accountants for a financially ruined country may have had more influence than the military. As we've seen, the British authorities weren't completely ignorant of the Hispano 20mm's capabilities. They had even seen that it was better to make the jump directly from .303s to 20mm armament, rather than hopscotch from .303s to .50cals and then to the bigger armament. Although some later Mark Spitfires and Bombers would use .50cals. In 1939, there had been plans to standardise armament efforts among the British and French, and adopt the Belgium FN version of the .50 caliber Browning machine gun. However, these plans were ruined when Belgium was invaded in 1940, and it seemed better to ramp up efforts to build .303 guns instead. This decision was probably made with expectations that suitable 20mm armament was only months away, rather than years. Supply was perhaps another reason why the .303 was favoured over the Browning .50 caliber. Although American industrial might was crucial in defeating the Axis powers, in 1939 it was still a sleeping giant. Had the British wanted to equip their entire air force with the machine gun in 1939, the Americans could not have provided the weapons. Vickers, a British company, also would probably have failed at this task. Rough figures suggest that from July 1940, production of all US built types of .50cal machine guns was about 5,155 guns. By 1941 they had produced 49,479 guns, and by 1945 factories knocked out about 239,821 guns. At the outbreak of war, almost immediately the .303 was shown to be somewhat inadequate. It's true that a .303 round was lethal when fired through an unarmoured aircraft panel, and its incendiary round version had double the chance of setting fuel tanks alight compared to a similar Axis round. Nevertheless, against ever more armoured enemy aircraft, which also began to be equipped with self-sealing fuel tanks, it was almost pitiful. Although a .303 reportedly could make it through up to 12mm of armour plate, it's effectiveness could be significantly reduced when it had to pass through other parts of an aircraft or if fired from extreme distance. Be that as it may, RAF and Commonwealth aircraft did manage to shoot down the enemy in droves, especially after tactics and harmonisation distances were improved. Would they have been more effective with similar armament of the later warbirds? Of course, but it takes time to refit air forces with better weapons. The British simply didn't have the industrial capability in 1940 to simply equip all their fighters and bomber aircraft with .50 calibre armament, let alone the 20mm Hispano cannon. What's more, the knowledge that a 20mm shell was more destructive was overshadowed by the difficulty of getting the gun to work reliably. When first trialled in RAF fighters, the Hispano HS404 was all but useless in combat, but this was largely because it wasn't used in the way it had been designed. First intended to be mounted around the engine on sturdy platforms, the guns were turned on their sides and installed in flexible and cold wings. This led to guns freezing and jamming. Even though the British had first been introduced to the gun in 1936, it took over 4 years for them to negotiate the rights to buy it, then to set up the subsidiary offices in Grantham, England to produce it, which then called for the gun to be redrawn in imperial measurements and tinkered with to produce a working and reliable armament. This was not done successfully until after the Battle of Britain, even though trials were made during the battle by 19th Squadron. These were not overly successful and the squadron even formally requested for the machine gun armed fighters to be returned. The issues faced by the Mk1 cannon armed Spitfires weren't really ironed out until the advent of the Mk5s in 1941. For bomber aircraft, the .303 remained the standard armament for various reasons, most importantly due to the delay in redesigning gun turrets. When a single machine gun was used, invariably it was the VGO. Although many American bombers would use a single .50 cal successfully in this role, the British didn't seem to want to re-equip the smaller bomber aircraft with them. However, by 1944, most aircraft in number one group of bomber command had been converted to carry the Rose Rice turret. This hydraulically powered turret boasted twin .50 cal machine guns and an open forward design which improved visibility and survivability for the gunner. However, the Air Ministry compiled a report that found that 60% of these turrets experienced stoppages compared to 23% of the older .303 armed turrets. It could be said that the .303 machine gun dictated RAF bomber command's tactics for most of WWII. The experiences of light bombers such as the Fairey Battles and even heavier types such as the Wellington over enemy territory in 1940, one thing was painfully clear. A handful of .303 machine guns could not ward off a gaggle of attacking German fighters. Almost immediately, the British opted for the relative safety of darkness to give them protection from the 109s and 110s. This also effectively relegated air gunners to the role of observer. Their job was less to engage the enemy and more to give advance warning so that evasive action could be taken. For the reduced distances that night fighting created, a .303 was effective enough. There was a perhaps apocryphal tale where Air Chief Marshal Harris, C&C of bomber command, was asked by an air gunner why they weren't given .50 cal machine guns instead of .303s. Harris replied, how far can you see at night on ops? About 300 yards was the reply. Exactly, says Harris. What's the point of having greater range if you cannot see the target? Perhaps a better point to make here is that the added weight of a .50 caliber machine gun would have to be compensated for with a reduced bomb or fuel capacity, especially in smaller bombers. The Hispano 20mm cannon really came into its own when the Mark 5 was developed and fitted to later production Hawker Tempest. However, this version of the Hispano 20mm didn't see widespread use in Spitfires until after the war. And the Spitfire is a very good example of the .303 being used throughout the entire war, whereas aircraft such as the Typhoon or Tempest were cannon armed and the Hurricane went through various armament configurations. Why did the British persist with cannon and .303 equipped Spitfires for much of the war? What is certain is that mounting twin 20mm cannons on Spitfires was not as easy as it was for Tempests or Typhoons. Preventing guns from freezing wasn't as easy, presumably because a significant part of the barrel was sticking out of the wing, especially when compared to the Tempests. Another reason might be due to an added bonus .303 ammunition provided a pilot when shooting at an enemy. The Dixon incendiary round, based on the Belgian De Waal design, tended to light up the impact zone when a round landed. These flashes were very helpful when trying to shoot down an enemy, as no similar incendiary round was developed to quite the same success for a .50 cal machine gun. Perhaps this was a deciding factor in keeping four .303 machine guns on most late war Spitfires. It's also true to say that the higher rate of fire the .303 provided was still effective when performing full deflection shots and could easily kill pilots or crew from this position. Another, if somewhat far-fetched opinion I uncovered, verges on some pretty in-depth game theory. Could the British have held onto their .303s simply because of the effect it had on Axis aircraft design? To explain this theory, let's look back a little further in history. Up until the late 17th century, most European armies fielded heavily armoured men. When armies grew in size, became more mobile and faced heavier firearms, armour was more of a hindrance. So, it was abandoned for the advantages it gave in the face of the protection it provided against swords and small arms fire. So, seeing that little could stop a 20mm shell, there would be little point in trying to protect a crew or fuel tank from it. However, when aircraft carry armament such as the .303 calibre machine gun, which is more easily protected against, it would be foolish not to install the armour plate. Although this seems a little far-fetched, it's essentially what the Japanese aircraft designers did during the run-up to war and what some Finnish units reportedly did during the war. Were the British really that canny? I'd love to hear what your thoughts on this theory is in the comments. If you've made it this far then please like the video to help it spread to more people and if you really want to support the channel then why not watch this next video right here. See you guys in the next one.