British .303 vs 50 Cal M2

[pinehilljoe]

Were Browning M2 50s ever considered as armament for British planes? The RAF seems to have settled on .303 rifle or 20 mm cannon for armament. Reading Korda's
With Wings Like Eagles, Korda credits Dowding for insisting on eight .303 minimum for the Hurricane and Spitfire. A Hurricane armed with 4 or 6 M2s would have been formidable in bringing down Heinkels.

 

[buffnut453]

The problem is that wing mounts for the M2 were only really perfected in late 1942. Every US fighter with wing-mounted 50cals suffered significant stoppage issues in the first 9-11 months of the war, mostly related to the ammo feed getting dislodged during aggressive manoeuvres. A fully-functioning battery of 6x50cals would, indeed, have been formidable but I don't think it was a practical proposition in 1939.

 

[pinehilljoe]

The problem is that wing mounts for the M2 were only really perfected in late 1942. Every US fighter with wing-mounted 50cals suffered significant stoppage issues in the first 9-11 months of the war, mostly related to the ammo feed getting dislodged during aggressive manoeuvres. A fully-functioning battery of 6x50cals would, indeed, have been formidable but I don't think it was a practical proposition in 1939.

Other than Lend Lease, the RAF seems to have kept the 20mm or 303 to the end of the War. Was the M2 ever consider for the later Hawker fighters?

 

[pinsog]

Weight was also an issue. 8 303's are about 200 pounds, 4 50's are 300 pounds. 6 50's is around 450 pounds, and that is too much weight for pre-1943 fighters to carry. None of this includes ammo, 50 caliber ammo is about 50 pounds per 200 rounds. US 30 caliber is 33 pounds for 500 rounds (303 should be very close)

 

[Shortround6]

We have been over this a bunch of times.
Yes six .50 cal Brownings from 1943 using 1943 ammunition would have been a vast improvement over the eight .303 guns and ammo of 1940.
The poor Hurricane might have struggled with the weight a bit though.
Roughly one .50 weighed as much as three .303s and the 100 rounds of .50 cal ammo weighs as much as 500 rounds of .303.

The .50 cal of 1939-40 was not the .50 cal of 1943 however. In addition to the above mentioned wing mount feed problems the the rate of fire was lower 600rpm at best vs around 800rpm and the ammo wasn't quite the same. The M8 API round wasn't introduced until 1943, while there were both AP rounds and incendiary rounds in 1939-40 you had to mix the rounds in the belts or have one gunfire one type while another gun fired the other type. The Incendiary bullet won't pierce armor and the AP bullet won't set fire to anything.

 

[pbehn]

Later Spitfires used 1x 0.5" gun mounted inside the cannon, in what was known as the "E" wing. I believe in the early pre war days things like security of supply played as much a part as considerations of hitting power.

The "e" wing was a further development of the Universal. It could carry either four 20mm cannon or two 20mm cannon and two 0.5in Browning machine guns. This time the cannon took the outer position and the machine guns the inner. This was partly because it gave more room for machine gun ammunition and partly because the bombs were carried below the inner gun positions, and there had been some problems reported when both cannon and bombs were on the same part of the wing. The "e" wing appeared in the second half of 1944.

 

[KiwiBiggles]

Other than Lend Lease, the RAF seems to have kept the 20mm or 303 to the end of the War. Was the M2 ever consider for the later Hawker fighters?

Why would it be? The US Navy's estimate was that the standard four 20 mm Hispanos in Hawker fighters were twice as powerful as a battery of six M2s.

 

[Clayton Magnet]

The RAF essentially skipped the step to heavy machine guns, and standardized on cannons as soon as possible. Something that took the AAF and later the USAF about 10 more years to do.

"A Hurricane armed with 4 or 6 M2s would have been formidable in bringing down Heinkels."
Keep in mind that the standard US fighter armament in 1939/40 was one .50 supported by one or two .30's.

 

[Shortround6]

Keep in mind that the standard US fighter armament in 1939/40 was one .50 supported by one or three .30's.

Fixed it.

 

[Clayton Magnet]

Fixed it.

thanks. I was thinking of the P-35, P-36 and F3F as examples

 

[Glider]

Also remember that before the war when aircraft lacked armour and sealing tanks 8 x 303 was a formidable combination

 

[J.A.W.]

AFAIR, the RAF determined 4 X 20mm Hispano as the 'standard fighter' fitment, ' bout 1940,
so specced 'their' Mustang with them, & regarded the Mustang III/P-51B/C fit - of 4 X 0.5in - as "light".

 

[parsifal]

I also think that the lighter rifle caliber weapons like the 0.303 in gun allowed greater amounts of ammunition to be carried, and this favoured relatively inexperienced pilots with less ammunition and less firing time. A rookie pilot will generally start firing earlier, take longer to begin to register on the target, if at all, and against un-armoured targets of 1939 a few 303s into the target might just be enough to bring the enemy down.

Later as armour and other protection became more or less standard, a fighter with greater punch was needed. When the ammunition supplies for 20mm were increased, such that the 20mm could fire for longer than a 0.50 the equation became a no-brainer.

 

[J.A.W.]

Pretty sure 20mm Hispano cannon ammo takes up a fair bit more space than 0.5in.
For A2G, generally gunnery 'time on target' was fairly limited so 'bursts' were more typical.

Footage of WW2 F6F's doing extended 'hosing' type firing runs on A2G was a different matter,
but AFAIR, part of the USN's reason for wanting to fit 20mm was due to those wily Nippon
infantry field engineers constructing basic tree-trunk bunkers - up to 0.5in 'proof standard'..

The 20mm Hispano would require 'an order of magnitude' - heavier protection level..

 

[Shortround6]

In 1940 a british 8 gun fighter was carrying about 254lbs of guns and about 160-186lbs of ammo (depending on 300 to 350 rpg to suit airplane. 2400-2800 rounds per plane)
The manual for a P-40D/E says that four .50 cal guns weigh 256lbs and 1000 round of ammo (250 per gun) weighs 300lbs.
The 6 guns on the P-40E went 384lbs with 1410 rounds of ammo (235 per gun) weighing 423lbs.
Given the power of the Merlin III engine which do you choose?
And remember they got constant speed props fitted just in the nick of time so many of these planes would have had 2 pitch props when built.

 

[J.A.W.]

Yes that'd be why the 'legacy' fighters, built to an ealier spec, had issues in toting 4 X 20mm.

The Hurricane had wingspace, but as SR6 noted on another thread, carried limited ammo.
The 1st Spitfires which featured 4 X 20mm - as standard, were the substantially re-designed, 1945 spec, 20-series..

 

[Shortround6]

Actually From the later MK Vs on they could have fitted 4 cannon if they wanted to, that was the whole idea of the "C" wing, it had the extra cannon bay built in and some MK V Spits on Malta got the 4 cannon., Insufficient gun heating and performance penalty stopped the fitting of 4 cannon until the 20 series.

 

[J.A.W.]

Exactly, 1st gen Spits were a bit light on it..

AFAIR, Spits for Malta were fitted with quad Hispanos, but 2 of these were 'spares',
& they were not flown in combat with them..

Some Australian Mk VIII's did tote 4 X 20mm, but this was for the A2G role,
with no Nippon A2A 'trade' in prospect, to make the perfomance penalty problematic..

 

[parsifal]

with 250 rpg of 0.5 in ammo, a gun has about 30 secs of continuous firing time. With 120 rounds per gun of 20mm ammo in belt fed versions of the weapon, there was about 1 minute of continuous firing available depending on the detail settings of the weapon. A 20mm shell does not need to hit a vital part to bring down an opponent, whereas a 0.5in still has to hit something essential

Like I said, a no brainer.

 

[Shortround6]

with 250 rpg of 0.5 in ammo, a gun has about 30 secs of continuous firing time. With 120 rounds per gun of 20mm ammo in belt fed versions of the weapon, there was about 1 minute of continuous firing available depending on the detail settings of the weapon. A 20mm shell does not need to hit a vital part to bring down an opponent, whereas a 0.5in still has to hit something essential

Like I said, a no brainer.

with 250 rounds
600rpm wing mounted .50 has 25 seconds firing time
800rpm wing mounted .50 has 18.8 seconds of firing time
500rpm synchronized .50 has 30 seconds firing time.
with 120 rounds
600rpm Hispano has 12 seconds.
with 300 rounds
a 1100rpm .303 had 16.4 seconds Adjust for Hurricane and Spit MK II & later.

The .50 ( and Russian 12.7mm) had wider range of possible targets in an aircraft than the .303 (or anybodies rifle caliber machine gun) because it could do more damage to the structure.
Holes right through structural components rather than gouges. Some BP tanks were good against rifle caliber fire but not against bigger holes. The .50 could cause seams to rupture on fuel tanks depending on size and how full they were. It could penetrate more armor (it could also fail spectacularly if the bullet hit something before the armor).
There were plenty of spaces on an aircraft where the .50 is going to go right through and just make a slightly bigger hole than the RCMG. But with the .50 things like longerons, spars, ribs, engine mounts and the like are much more likely to suffer major damage.
Now everything I just said about the .50 gets multiplied for the Hispano 20mm even if the Hispano is firing ball ammo (non exploding) or the fuse fails to function.

BTW the weights I gave earlier for the British .303 and the American .50 are a bit skewed. The .303 weights are from a weights and loading chart for a Spitfire and may very well represent the .303 s as installed. many charts/descriptions use a lighter weight.
The weight for the .50s, on the other hand, are about as light as I have ever seen. Early F4F with four guns and 200rpg has a weight of 524.5lbs.
Things like gun heaters, charging/cocking systems and even firing solenoids are sometimes counted and sometimes not.