British .303" (7.7mm) Browning guns:
8 machine guns mounted in wings (outside the propeller disk)
20 rounds per second per gun (160 rounds per second overall)
11.3 gram bullets fired at 740 m/s (2,430 fps)
16 seconds worth of ammunition
Bf109s MG 17s (7.9mm) machine guns:
2 machine guns mounted in the engine cowling (synchronised to shoot through the propeller disk)
17 rounds per second per gun (slower because of sync with propeller)
Slightly more destructive than the .303s (bullet mass and muzzle velocity varied)
1 minutes worth of ammunition
Bf109E-4 20mm MG-FFM cannon:
2 mounted in wings
9 rounds per second per cannon (18 rounds per second overall)
92 gram explosive projectiles fired at 700 m/s
Less than 7 seconds worth of ammunition
Comparison
Spitfires and Hurricanes had 8x .303" Browning machine guns mounted in the wings where as the Bf109 had 2x machine guns mounted in the engine cowling shooting through the propeller disk.
The Bf109 machine guns could not fire as quickly as the Browning machine guns because they had to synchronise with the propeller.
The British fighters had to have their guns adjusted so they harmonised at a single point at a predetermined distance from the aircraft (360m at the start of the Battle and reduced to 225m due to battle experience). This meant they were only at their most destructive at this single distance. The Bf109 machine guns were effective over a much broader ranger because they were so close to the centre-line of the aircraft.
The Bf109 machine guns were slightly more destructive than the British Brownings but could carry nearly a minute's worth of ammunition rather than the 16 seconds carried by a Spitfire.
The Bf109E-4 cannon, with its explosive projectile, was much more destructive than the Brownings but had a much slower firing rate (9 rounds per second instead of the Brownings' 20 rounds per second) and only had 7 seconds worth of ammunition on board.
The Bf109E-4 cannon had a long flight time and curved trajectory (due to its low muzzle velocity) which made it difficult to hit targets at distance. It was quite a challenge for the German pilots because the flight times and trajectory curves of the cannon and machine guns were different requiring different mental calculations during combat.
How Did This Play Out In Combat?
It was much easier for a Spitfire or Hurricane to hit something with its eight fast firing Brownings than it was for a Bf109 with its slow, difficult to aim cannon with only 7 seconds of ammunition.
but...
if a Bf109E-4 hit its target could cause an immense amount of damage.
Many a German aircraft would be riddled with .303 bullet holes but still return to base.
The RAF committed to fitting its Spitfires and Hurricanes with .303 machine guns well before WW2 when aircraft were slower and less well armoured. By the time of the Battle of Britain the RAF knew they needed much more powerful armaments. They tried to hurry in the fitting of 20mm Hispano cannons but they weren't reliable until after the Battle had ended.
So Which Guns Were Best?
Lesser pilots would find it easier to hit their target flying a British fighter than a Bf109
Better pilots would find it easier to bring down their target flying a Bf109
Whilst the guns would seem to have been better in the German aircraft, perhaps fortune favoured the British solution in a battle of attrition where, as time went on, experienced pilots were shot down and replaced with less experienced pilots.
by Steve Dunster
I have to add something. Even if 20mm cannon shell was more destructive, 4-5 were need to destroy Spitfire or Hurricane or one in perfect place. Many british fighters came back to force-land being damaged by cannon fire. Me 109 was easy to destroy especially by hitting colling system and engine. One was shot down by ONE bullet into cooling and forced to land on british soil by RAF fighter.
ReplyDeleteOnly good pilots or pilots with luck could destroy RAF fighter by cannon and MG fire, too many were only damaged!