davebender
1st Lieutenant
BoB era Me-109s and Spitfires quickly ran out of fuel. 60 rounds might be enough for 15 minutes of combat. Aircraft that carry more internal fuel also need to carry more ammunition.
What was the air to air weapon, or combination of weapons, used in WWII?
- Thread starter CobberKane
- Start date
Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
Shortround6
Major General
60 rounds was nowhere near enough for 15 minutes of combat. 60 rounds was good enough for 7-8 seconds of firing time after which the 109E had over 850 rounds of 7.9mm ammo left for each MG 17.
Spitfire MK Is carried about 17 seconds worth of ammo.
A one second burst is pretty much useless for most pilots. One second on target might be all it takes to inflect damage but it takes some time to get on target and around 1/3 to 1 second to stop firing at the end. Firing pilot realizes he is hitting AND has inflicted enough damage takes a few tenths of second. The time of flight may be .3 or so? SO pilot is seeing damage (flames) with .3 sec worth of shells in the air and still has to release the trigger. The British were averaging about 17 shots per gun per burst from the Hispano guns near the end of the war. 60 shells is enough for 3-4 bursts. Maybe a fighter only gets 3-4 firing opportunities in 15 minutes, maybe it gets 4 firing opportunities in 2 minutes.
Spitfire MK Is carried about 17 seconds worth of ammo.
A one second burst is pretty much useless for most pilots. One second on target might be all it takes to inflect damage but it takes some time to get on target and around 1/3 to 1 second to stop firing at the end. Firing pilot realizes he is hitting AND has inflicted enough damage takes a few tenths of second. The time of flight may be .3 or so? SO pilot is seeing damage (flames) with .3 sec worth of shells in the air and still has to release the trigger. The British were averaging about 17 shots per gun per burst from the Hispano guns near the end of the war. 60 shells is enough for 3-4 bursts. Maybe a fighter only gets 3-4 firing opportunities in 15 minutes, maybe it gets 4 firing opportunities in 2 minutes.
Last edited:
Shortround6
Major General
A few points about aircraft armament since "There Is No Such Thing As A Free Lunch".
1. Light weight guns have to paid for either in low performance or low durability or both.
2. Guns are not laser beams. they fire a "pattern" or group which gets larger with range.
3. Most combat evaluations depend on an AVERAGE, some pilots do better or much better, some pilots do worse. Biasing armament too much one way or another has to be paid for.
4. While looking at fighters with thousands (if not tens of thousands) built with minimal armament one also has to consider what was "wanted" but not fitted due to other considerations, like lack of space or lack of engine power.
to elaborate a bit, take point #1. The US Browning .50 did the job in WW II but was far from ideal. It was heavy for it's power but the weight meant it was fairly reliable (the gun more than the feed mechanism/arrangements) and durable. Changing the barrel and a few minor parts might allow for a life of 10-20,000 rounds if not more. The Russian 12.7mm gun had a life closer to 2500 rounds. It was much lighter which allowed for higher performance of the planes carrying it. Many planes get shot down (or crash) well before reaching 2500 rounds fired. BUT many do not. B-17s or B-24s could easily fire 2500-5000 rounds from some of their guns in just 5-10 missions. Having to provide replacement guns in such numbers might be a problem. Having just one gun for most applications also simplified training of armorers, manufacture, supply of parts and ammunition. The US had the longest ( and perhaps the most complicated) supply lines of the major combatants of WW II. These "attributes" don't show up in a simple comparison of weights, rate of fire, velocity and projectile weight. The US was "blessed" with high powered engines and could afford better than most to use guns that were down on the weight/power efficiency scale.
Point#2. in order to get lethal concentrations of fire at longer ranges ( and in aircraft longer range could be 400yds instead of 200 yds) more rounds per second are needed. Either higher rate of fire guns or more guns. You also have the time of flight problem which was mentioned by others. The US spent a considerable amount of time and money trying for even higher velocity than the .50 Browning had because they thought it would considerable increase the hit potential.
more later.
1. Light weight guns have to paid for either in low performance or low durability or both.
2. Guns are not laser beams. they fire a "pattern" or group which gets larger with range.
3. Most combat evaluations depend on an AVERAGE, some pilots do better or much better, some pilots do worse. Biasing armament too much one way or another has to be paid for.
4. While looking at fighters with thousands (if not tens of thousands) built with minimal armament one also has to consider what was "wanted" but not fitted due to other considerations, like lack of space or lack of engine power.
to elaborate a bit, take point #1. The US Browning .50 did the job in WW II but was far from ideal. It was heavy for it's power but the weight meant it was fairly reliable (the gun more than the feed mechanism/arrangements) and durable. Changing the barrel and a few minor parts might allow for a life of 10-20,000 rounds if not more. The Russian 12.7mm gun had a life closer to 2500 rounds. It was much lighter which allowed for higher performance of the planes carrying it. Many planes get shot down (or crash) well before reaching 2500 rounds fired. BUT many do not. B-17s or B-24s could easily fire 2500-5000 rounds from some of their guns in just 5-10 missions. Having to provide replacement guns in such numbers might be a problem. Having just one gun for most applications also simplified training of armorers, manufacture, supply of parts and ammunition. The US had the longest ( and perhaps the most complicated) supply lines of the major combatants of WW II. These "attributes" don't show up in a simple comparison of weights, rate of fire, velocity and projectile weight. The US was "blessed" with high powered engines and could afford better than most to use guns that were down on the weight/power efficiency scale.
Point#2. in order to get lethal concentrations of fire at longer ranges ( and in aircraft longer range could be 400yds instead of 200 yds) more rounds per second are needed. Either higher rate of fire guns or more guns. You also have the time of flight problem which was mentioned by others. The US spent a considerable amount of time and money trying for even higher velocity than the .50 Browning had because they thought it would considerable increase the hit potential.
more later.
davebender
1st Lieutenant
So did Germany. The MG151/15 has to be one of the longest range machineguns ever made. 15mm x 96mm AP(WC) rounds achieved 1,030 meters per second.
Shortround6
Major General
It would be a lot more useful in advancing discussions (instead of advancing an agenda) if you quoted general purpose figures instead of special purpose or limited issue ammunition ( or guns, as the case may be).
There is some debate as to wither the MG151/15 is a cannon or a machine gun despite it's nomenclature.
The 15mm x 96mm AP ammunition with the 1,030 m/s muzzle velocity is a APCR round with a weight of 52 g (compared to the 72g weight of the normal AP projectile) and it may not hold it's velocity or range as well as the normal ammunition. Most APCR did not.
As for "one of the longest range machineguns ever made" it may have just a bit of trouble even matching the Czech ZB vz/60 (15mm BESA) let alone the Soviet 14.5mm gun. It rather depends on the actual shape of the projectiles involved. And that is for service guns. The US experimental cartridges which include the 20mm Hispano necked to .50 and .60 cal and the .60 cal case itself (later necked out to 20mm for the 20mm Vulcan gun) can both well exceed the German figures as can the Belgian commercial 15mm and 15.5mm commercial offerings.
Not only were these American HV MGs extremely heavy for their hitting power ( being the size of or even larger than 20mm Hispano guns) but still using non-exploding ammunition and they burned out barrels at an alarming rate. They traded higher likelyhood of hitting for the destructive power of 20mm shells once they had gotten a hit.
Last edited:
Re. Zero's armament: it was far away from the ideal set up, until it received belt fed, more powerful cannons. Same things apply as for the Bf-109Es.
Yep, three B-20 cannons were mounted in number of La-7.
La-9 simply serves as an example - 4 cannons (mostly/always in 23mm calibre?) in the nose were very much feasible for the ww2 technology.
Yep, three B-20 cannons were mounted in number of La-7.
La-9 simply serves as an example - 4 cannons (mostly/always in 23mm calibre?) in the nose were very much feasible for the ww2 technology.
Last edited:
parsifal
Colonel
Which means these aircraft were all penalised by the extra weight of the wepons fit. A four gun broadside carrying 430 rounds is heavier than a 6 gun broadside carrying 240 rpg.
An interesting aside. The RN tactics with the 6 gun broadside was generally not to fire all six guns simultaneously. The two outboard guns could be fired separately, as a result most FAA pilots used these two outboard guns as an emergency supply. RN was also first to develop LR tankage for the type, jury rigged by field mods in 1941.
I agree, but is it worth quatering you firepower per gun. I dont think that it does, and post war, most navies, including the USN tended to agree
I agree, especially trying to marry two such dissimilar weapons as the 7.7 and Type 99-1. Might explain why the later marks of Zero partially chganged riflre mounted armament to 13.2mm guns.
Small correction. There were actually 1389, if the 220 Martlet IVs are included
All of these are contradicting requirements - a "lethal" concentration of fire requires the guns to have the least amount of spread, or exponentially increased number of rounds fired and rely on chance. Increasing muzzle velocity and general ballistic quality of gun WILL, on the other INCREASE the gun's spread exponentially on an automatic gun, means that the high velocity gun may have less time to travel to distance, but at the same time it will also score less hits because of greater spread, provided the aim point is correct. But if it's not, what is the pont of a supposedly long range gun, if you are just firing it off blind...?
Many did try out various guns with high ballistic capacity, but in the end everyone seem to have realize sooner or later the correct answer is to settle with a gun good enough for about 200 meters, and make it as light and fast firing as possible. See MG 151 -> MG 151/20, MK 103 -> MK 108, Hispano II -> Hispano V, Schwak -> B-20 etc.
Last edited:
Why does everyone always have to accuse everyone of having an agenda? Not trying to single anyone out here. It is just a common thing in these parts. 
Just discuss the topic and let the facts speak for themselves, whatever the facts may be.
In the end the facts and truth always come out...
Just discuss the topic and let the facts speak for themselves, whatever the facts may be.
In the end the facts and truth always come out...
Shortround6
Major General
Getting back to:
Point #3. a heavy armament ( in installed weight) benefits pilots who are poorer shots, have had less training/experience or are facing larger/heavier aircraft. Or combinations of the above. Depending on ammo supply the heavy armament can also provide longer firing times providing longer combat duration ( more intercepts/firing opportunities) per flight. It is payed for by poorer climb and maneuverability. A light armament gives the opposite, better climb and maneuverability but less combat duration and/or hitting power. With well trained pilots the light armament can be made to work against fighters and small bombers. But too heavy an armament for a given engine and the plane cannot get into firing position quickly or easily (if at all). It is all a trade off.
#4. Ties in with the above. The Russians wanted more guns/ammo for the Lagg-3, Yak series but their inability ( for a number of reasons) to get more power from the 105 series of engines meant that heavier armament cut into performance too much.
Point #3. a heavy armament ( in installed weight) benefits pilots who are poorer shots, have had less training/experience or are facing larger/heavier aircraft. Or combinations of the above. Depending on ammo supply the heavy armament can also provide longer firing times providing longer combat duration ( more intercepts/firing opportunities) per flight. It is payed for by poorer climb and maneuverability. A light armament gives the opposite, better climb and maneuverability but less combat duration and/or hitting power. With well trained pilots the light armament can be made to work against fighters and small bombers. But too heavy an armament for a given engine and the plane cannot get into firing position quickly or easily (if at all). It is all a trade off.
#4. Ties in with the above. The Russians wanted more guns/ammo for the Lagg-3, Yak series but their inability ( for a number of reasons) to get more power from the 105 series of engines meant that heavier armament cut into performance too much.
Shortround6
Major General
True.
The B-20 weighed 25KG compared to the older ShVAK 20m canon weighing 42KG. The NS-23 weighed 37kg???
Armament (according to WIKI????) for an LA-7 was 2 ShVAK ( or B-20s?) with 200rpg or 3 B-20s with 100rpg.
The LA-9 with 4 NS-23 carried 75rpg??
LA-9 was a totally new airframe that just looked something like a LA-7.
The LA-9 had tremendous firepower but it's combat duration was none too good. 8 seconds firing time?
- Thread starter
- #32
CobberKane
Banned
- 706
- Apr 4, 2012
This seems to me to be the best characterisic of the .50s used in the P-51 and P-47. Either plane would have received a significant boost in firepower if fitted with cannon, but at the expense of ammunition load. The .50 was perhaps a bit over-hyped by might USAAF pilots who never had to face heavy bombers, but it was fine against single and twin-engined aircraft, reliable and enabled the Mustang and P-47, and especially the P-38, heaps of firing time - very important if you have to protect bombers of enemy territory for several hours
Shortround6
Major General
Why? What would make the spread 4 times greater by doubling the muzzle velocity?
It could happen but something sounds wrong with the set up. Weird barrel vibration, poor mounting, excessive "bouncing" or battering as the bolt goes back and forth. A lot of this can be "tuned" out. Wrong rifling twist for the projectile/velocity used?
Less time to travel the distance means that the aiming point is closer to the target. Before the deployment of good gyro gunsights (and radar ranging in Korea) the biggest problem in deflection shooting was figuring out the proper aiming point. The high velocity gun reduces this aim off error ( it does not eliminate it), a super tight grouping gun does no good if it is aimed at the wrong spot, it too, is being fired "blind".
The last two examples are not really examples. Each pair uses the same ammo and for all practical purposes have the same effective MV and range. The MK V Hispano had 96.6% of the muzzle velocity of the MK II.
parsifal
Colonel
We tend not to think about the weight penalties of a particular armament installation. Ive given those for the Wildcat and the Zero (and frankly was surprised that the F4F3 carried a greater weight penalty because of the additional ammunition carried. The F4F3 had a 34 second burst, which is not too bad. Somebody also said the Spitfire I had a 20 second burst. I havent cross checked that, but did find that the 8x 303s plus armament on the Spit amounted to 685 lbs. Thats quite a weight penalty for an armament even less lethal than the F4F, and worse, with even less burst time.
I wonder what the 109 weight penalties were .....
Shortround6
Major General
I am not sure where you got the 685lb figure for the Spitfire?
See: Spitfire Mk IX Weights and Loading
439.5 lbs for eight .303s with 350rpg. MK I Spitfires had 300rpg?
664lb for four .303s (and I added 14.5lbs to the weight in the chart) and two 20mm guns.
A full load of .50cal ammo for a 4 gun Wildcat was 1720 rounds, which was 516lbs just for ammo (give or take depending on bullet type/belt mix) the four .50s weighed another 286lbs. Some Navy performance figures or weight charts show as little as 360lbs of ammo (300rpg?). The six gun version shows 433lbs for the guns ( different accessory than the 420lb weight? different solenoid or charging system? Not enough to worry about) with a full ammo load of 1440 rounds or 432lbs of ammo.
Fro your last question see: WORLD WAR 2 FIGHTER GUN EFFECTIVENESS
and go to table 3.
109E--------149KG
109F-4------129KG
109G-6/R6---286KG
I would note however that these weights are JUST for the guns and ammo. as Tony's site says in the notes "It does not include belt links, ammunition tanks, gun mounting points and recoil buffers, synchronisation systems and trigger gear, et cetera. Realistic figures for the weight penalty would probably be 30 to 60% higher".
as an example he gives the weights of a MK Vc Spitfire at 235kg (517lbs?) which should be the same as the MK IX table given above. Weights for Hispano guns are often given for the bare gun and do not include the belt feed mechanism and a few other bits and pieces, like the cocking/charging mechanism and firing system.
See: Spitfire Mk IX Weights and Loading
439.5 lbs for eight .303s with 350rpg. MK I Spitfires had 300rpg?
664lb for four .303s (and I added 14.5lbs to the weight in the chart) and two 20mm guns.
A full load of .50cal ammo for a 4 gun Wildcat was 1720 rounds, which was 516lbs just for ammo (give or take depending on bullet type/belt mix) the four .50s weighed another 286lbs. Some Navy performance figures or weight charts show as little as 360lbs of ammo (300rpg?). The six gun version shows 433lbs for the guns ( different accessory than the 420lb weight? different solenoid or charging system? Not enough to worry about) with a full ammo load of 1440 rounds or 432lbs of ammo.
Fro your last question see: WORLD WAR 2 FIGHTER GUN EFFECTIVENESS
and go to table 3.
109E--------149KG
109F-4------129KG
109G-6/R6---286KG
I would note however that these weights are JUST for the guns and ammo. as Tony's site says in the notes "It does not include belt links, ammunition tanks, gun mounting points and recoil buffers, synchronisation systems and trigger gear, et cetera. Realistic figures for the weight penalty would probably be 30 to 60% higher".
as an example he gives the weights of a MK Vc Spitfire at 235kg (517lbs?) which should be the same as the MK IX table given above. Weights for Hispano guns are often given for the bare gun and do not include the belt feed mechanism and a few other bits and pieces, like the cocking/charging mechanism and firing system.
parsifal
Colonel
I found the information on a webpage do you think I can find it again....it had a green background. I dont mind being corrected, and take the point that we should compare apples to apples. Stanadard load out for the 303 in the A wing was 300rpg, as you say, so really to make our own comparison of "apples to apples" I would think we need to add up the weight of guns plus the ammo loadout. Foreget the other bits, all we are looking at are the guns and the bullets.
- Thread starter
- #37
CobberKane
Banned
- 706
- Apr 4, 2012
I've got a couple of other points that I'd be interested to hear some views on
1. I understand that past a certain point the Spitfire was built with a 'universal' wing anble to house three armment options: 2x20mm+4x.303, 2x20mm+2X.50 or 4x20mm. Yet the first option seems to have been far and away the most common. Did the ability of the 20mms to bust holes in self sealing tanks and engine blocks then make the many small incendiary rounds from the .303 much more dangerous?
2. Is it true that one reason the Americans never really adopted the 20mm en mass was that the cannons they manufactured were less reliable then the British equivilents?
1. I understand that past a certain point the Spitfire was built with a 'universal' wing anble to house three armment options: 2x20mm+4x.303, 2x20mm+2X.50 or 4x20mm. Yet the first option seems to have been far and away the most common. Did the ability of the 20mms to bust holes in self sealing tanks and engine blocks then make the many small incendiary rounds from the .303 much more dangerous?
2. Is it true that one reason the Americans never really adopted the 20mm en mass was that the cannons they manufactured were less reliable then the British equivilents?
parsifal
Colonel
I found this discussion on Tony williams' site regarding the use of the 50 cal in US aircraft
"The end of 1941 also saw America and Japan enter the war. Their aircraft weapons were very different. America relied almost entirely on the Browning machine-gun, not just in .50 (12.7 mm) calibre, but, for the first couple of years, in .30 (7.62mm) as well. The Japanese army and navy air forces followed their own paths, the army steadily up-gunning from 7.7 mm through 12.7 mm machine-guns and later 20 mm cannon, with 30 mm and even larger guns seeing limited service by the end of the war. The navy started with a mixture of 7.7mm MGs and Type 99 (Oerlikon) 20 mm cannon and continued to rely on this cannon (initially the low-velocity Type 99-1, later the more powerful Type 99-2), although it did make some use of HMGs and was also introducing 30 mm guns by the end of the war. As in Germany, the destruction of American heavy bombers was a strong incentive for the development of weapons of 30 mm or larger calibre.
The Americans did not intend to make such a commitment to the Browning MGs. Both before and during the war considerable efforts were made to secure alternative aircraft guns. Trials of foreign equipment resulted in the selection of the 20 mm Hispano-Suiza HS 404, large numbers being made. The Browning-designed 37 mm M4 cannon was also introduced, although used almost exclusively by the Bell P-39 and P-63. However, the standard fighter armament became a battery of six .50 inch Browning M2 HMGs.
This has led to the often-expressed view that the .50 inch M2 was the best all-round fighter gun of the war. After all, the USAAF and US Navy fighters unquestionably came to dominate the skies in which they fought. If there had been a better gun, America would have used it. However, the truth is not quite as simple as that. There are two issues here; how good was the .50 M2 compared with other HMGs, and how effective was it compared with cannon?
The most obvious comparator was the Soviet UB, which fired ammunition of virtually identical power. The UB weighed 25 kg, compared with the M2's 29 kg, but the Soviet gun fired at 17.5 rps, compared with around 13 for the M2. In terms of power- to-weight ratio the Berezin was therefore clearly superior. The Browning fared better against most other HMGs, as they all fired less-powerful ammunition, so the M2 enjoyed advantages in range and penetration. However, it had a slightly lower rate of fire than the German and Japanese guns (both around 15 rps), and was also bigger and heavier. The most powerful of all of the HMGs was the 15 mm MG 151, but this was heavier and slower-firing than the M2. Overall, therefore, the .50 M2 was not the best of the HMGs but was about average, with reasonable performance for its weight.
How did HMGs compare with 20 mm cannon? The first problem is that the cannon varied hugely in size, weight and performance. The MG*FFM, Type 99-1 and B-20 were all lighter than the M2, but the first two were significantly worse in terms of muzzle velocity and rate of fire, although the B-20 matched the M2's rate of fire and was not far behind in velocity. The Japanese Ho-5 and Type 99-2 and the ShVAK and MG 151/20 were all somewhat heavier. Muzzle velocities and rates of fire were closer to the M2's but generally still not as good. The Hispano was significantly heavier and slower-firing until the British Mk V emerged near the war's end, matching the MG 151/20 in weight and rate of fire.
The foregoing compares only the guns' efficiency; it takes no account of ammunition, the area in which the HMG loses most ground. The 20 mm cannon shells were not only two to three times heavier than HMG bullets, but their HEI contents greatly increased their effectiveness. Although HE ammunition was available for most HMGs, their small bullets severely limited the quantity of chemicals carried, so the Americans decided not to use them. Initially, the M2 used a mix of incendiary and AP bullets, with some tracers, but in 1944 the M8 API began to take over. Rather curiously, this was based on the Soviet B.32 API used in the Berezin.
It is difficult to assess the effectiveness of different ammunition types, but various tests suggest that a typical World War Two-era HE or incendiary shell, with chemical contents forming about 10 per cent of total shell weight, was about twice as destructive as a plain steel shell of similar size and weight. This makes it clear that 20 mm cannon were considerably more destructive for a given total weight of armament than any HMG could hope to be. For example, the .50 M8 API contained less than one gram of incendiary, whereas the 20 mm Hispano SAPI achieved similar armour penetration but carried more than ten times as much incendiary material.
This advantage was recognised by the US Navy. After comparing the .50 M2 and the 20 mm Hispano they estimated that the cannon was three times as effective. In other words, the typical RAF armament of four 20 mm cannon was twice as destructive as the USAAF's six .50 HMGs, for very little more weight. Proponents of the Browning HMG point to its excellent ballistics, which enhanced its range and hit probability. But the Hispano's muzzle velocity was very similar, and although the blunt-nosed shells were less aerodynamic the difference over typical air-combat ranges was not significant.
The cannon's advantages are clearly shown in the decisions made as a result of combat experience by air forces with a choice of good HMGs and cannon. We have already seen how Germany preferred the 20 mm version of the MG 151 despite its poorer ballistics. In the 12.7 mm Berezin the Soviets had arguably the best HMG of the war, but they still preferred the heavier, slower-firing 20 mm ShVAK. Japan had several good HMGs available; the army's Ho-103, and the navy's 13 mm Type 3, a .50 Browning chambered for slightly larger-calibre ammunition, but they made increasing use of cannon.
So why did the Americans not make more use of cannon, specifically the 20 mm Hispano they already had in mass production? There were two main reasons. One was certainly that the M2 was adequate for its purpose. In Western Europe the main adversaries were fighters, which were much easier to damage and shoot down than bombers. In the Pacific Theatre the Japanese aircraft were initially poorly protected and easy to shoot down. Later Japanese aircraft were better protected, but again these were usually fighters. If the Americans had faced the need to stop raids by heavy, well-protected bombers, it is likely that the HMG's shortcomings would have been starkly revealed.
There was another reason, however, which explains why the US Navy, despite rating the cannon very highly and facing the need to deal with attacking bombers and kamikazes, fitted it to few aircraft. That was serious production prob*lems with the American Hispano, which gave it a reputation for unreliability. Despite production running well into six figures, the American Hispano failed to achieve an acceptable reliability standard for the duration of the war.
To return to the original question, were the Americans right to rely so heavily on the .50 M2 when all other combatant nations had a clear preference for cannon of at least 20 mm calibre? The answer has to be yes. It was adequate for its purpose, and was the only satisfactory aircraft gun in production in the USA. It was very reliable (except where the installations created problems), was made in huge quantities, and the simplification of supply by comparison with the diversity of weapons used by the Axis powers gave a major logistical advantage. However, the Americans could get away with using a weapon so deficient in destructive power not only because of the nature of their opposition, but also because the size and engine power of their fighters enabled them to carry a battery of at least six guns, thus making up in quantity what they lacked in destructive quality.
The advantages of the 20 mm Hispano M2 were not entirely ignored. It was carried by Lockheed P-38s, together with four .50 Brownings. It was also installed in nightfighters, which needed maximum firepower to convert a short firing opportunity into a kill. Four were installed in Northrop's P-61 Black Widow, and two could be mounted in a Grumman F6F-5N. The cannon's extra firepower was also appreciated for ground strafing.
After the war the US Navy quickly changed over to the 20 mm cannon in its improved, faster-firing and more reliable M3 form, but the USAF stayed with the .50 M3 until the fighting in Korea demonstrated once and for all that the HMG had had its day. From the mid-1950s the USAF at last replaced the old Browning with 20 mm cannon, initially the M39 revolver and then the M61 rotary - just as most of the rest of the world was moving up to 30 mm!"
"The end of 1941 also saw America and Japan enter the war. Their aircraft weapons were very different. America relied almost entirely on the Browning machine-gun, not just in .50 (12.7 mm) calibre, but, for the first couple of years, in .30 (7.62mm) as well. The Japanese army and navy air forces followed their own paths, the army steadily up-gunning from 7.7 mm through 12.7 mm machine-guns and later 20 mm cannon, with 30 mm and even larger guns seeing limited service by the end of the war. The navy started with a mixture of 7.7mm MGs and Type 99 (Oerlikon) 20 mm cannon and continued to rely on this cannon (initially the low-velocity Type 99-1, later the more powerful Type 99-2), although it did make some use of HMGs and was also introducing 30 mm guns by the end of the war. As in Germany, the destruction of American heavy bombers was a strong incentive for the development of weapons of 30 mm or larger calibre.
The Americans did not intend to make such a commitment to the Browning MGs. Both before and during the war considerable efforts were made to secure alternative aircraft guns. Trials of foreign equipment resulted in the selection of the 20 mm Hispano-Suiza HS 404, large numbers being made. The Browning-designed 37 mm M4 cannon was also introduced, although used almost exclusively by the Bell P-39 and P-63. However, the standard fighter armament became a battery of six .50 inch Browning M2 HMGs.
This has led to the often-expressed view that the .50 inch M2 was the best all-round fighter gun of the war. After all, the USAAF and US Navy fighters unquestionably came to dominate the skies in which they fought. If there had been a better gun, America would have used it. However, the truth is not quite as simple as that. There are two issues here; how good was the .50 M2 compared with other HMGs, and how effective was it compared with cannon?
The most obvious comparator was the Soviet UB, which fired ammunition of virtually identical power. The UB weighed 25 kg, compared with the M2's 29 kg, but the Soviet gun fired at 17.5 rps, compared with around 13 for the M2. In terms of power- to-weight ratio the Berezin was therefore clearly superior. The Browning fared better against most other HMGs, as they all fired less-powerful ammunition, so the M2 enjoyed advantages in range and penetration. However, it had a slightly lower rate of fire than the German and Japanese guns (both around 15 rps), and was also bigger and heavier. The most powerful of all of the HMGs was the 15 mm MG 151, but this was heavier and slower-firing than the M2. Overall, therefore, the .50 M2 was not the best of the HMGs but was about average, with reasonable performance for its weight.
How did HMGs compare with 20 mm cannon? The first problem is that the cannon varied hugely in size, weight and performance. The MG*FFM, Type 99-1 and B-20 were all lighter than the M2, but the first two were significantly worse in terms of muzzle velocity and rate of fire, although the B-20 matched the M2's rate of fire and was not far behind in velocity. The Japanese Ho-5 and Type 99-2 and the ShVAK and MG 151/20 were all somewhat heavier. Muzzle velocities and rates of fire were closer to the M2's but generally still not as good. The Hispano was significantly heavier and slower-firing until the British Mk V emerged near the war's end, matching the MG 151/20 in weight and rate of fire.
The foregoing compares only the guns' efficiency; it takes no account of ammunition, the area in which the HMG loses most ground. The 20 mm cannon shells were not only two to three times heavier than HMG bullets, but their HEI contents greatly increased their effectiveness. Although HE ammunition was available for most HMGs, their small bullets severely limited the quantity of chemicals carried, so the Americans decided not to use them. Initially, the M2 used a mix of incendiary and AP bullets, with some tracers, but in 1944 the M8 API began to take over. Rather curiously, this was based on the Soviet B.32 API used in the Berezin.
It is difficult to assess the effectiveness of different ammunition types, but various tests suggest that a typical World War Two-era HE or incendiary shell, with chemical contents forming about 10 per cent of total shell weight, was about twice as destructive as a plain steel shell of similar size and weight. This makes it clear that 20 mm cannon were considerably more destructive for a given total weight of armament than any HMG could hope to be. For example, the .50 M8 API contained less than one gram of incendiary, whereas the 20 mm Hispano SAPI achieved similar armour penetration but carried more than ten times as much incendiary material.
This advantage was recognised by the US Navy. After comparing the .50 M2 and the 20 mm Hispano they estimated that the cannon was three times as effective. In other words, the typical RAF armament of four 20 mm cannon was twice as destructive as the USAAF's six .50 HMGs, for very little more weight. Proponents of the Browning HMG point to its excellent ballistics, which enhanced its range and hit probability. But the Hispano's muzzle velocity was very similar, and although the blunt-nosed shells were less aerodynamic the difference over typical air-combat ranges was not significant.
The cannon's advantages are clearly shown in the decisions made as a result of combat experience by air forces with a choice of good HMGs and cannon. We have already seen how Germany preferred the 20 mm version of the MG 151 despite its poorer ballistics. In the 12.7 mm Berezin the Soviets had arguably the best HMG of the war, but they still preferred the heavier, slower-firing 20 mm ShVAK. Japan had several good HMGs available; the army's Ho-103, and the navy's 13 mm Type 3, a .50 Browning chambered for slightly larger-calibre ammunition, but they made increasing use of cannon.
So why did the Americans not make more use of cannon, specifically the 20 mm Hispano they already had in mass production? There were two main reasons. One was certainly that the M2 was adequate for its purpose. In Western Europe the main adversaries were fighters, which were much easier to damage and shoot down than bombers. In the Pacific Theatre the Japanese aircraft were initially poorly protected and easy to shoot down. Later Japanese aircraft were better protected, but again these were usually fighters. If the Americans had faced the need to stop raids by heavy, well-protected bombers, it is likely that the HMG's shortcomings would have been starkly revealed.
There was another reason, however, which explains why the US Navy, despite rating the cannon very highly and facing the need to deal with attacking bombers and kamikazes, fitted it to few aircraft. That was serious production prob*lems with the American Hispano, which gave it a reputation for unreliability. Despite production running well into six figures, the American Hispano failed to achieve an acceptable reliability standard for the duration of the war.
To return to the original question, were the Americans right to rely so heavily on the .50 M2 when all other combatant nations had a clear preference for cannon of at least 20 mm calibre? The answer has to be yes. It was adequate for its purpose, and was the only satisfactory aircraft gun in production in the USA. It was very reliable (except where the installations created problems), was made in huge quantities, and the simplification of supply by comparison with the diversity of weapons used by the Axis powers gave a major logistical advantage. However, the Americans could get away with using a weapon so deficient in destructive power not only because of the nature of their opposition, but also because the size and engine power of their fighters enabled them to carry a battery of at least six guns, thus making up in quantity what they lacked in destructive quality.
The advantages of the 20 mm Hispano M2 were not entirely ignored. It was carried by Lockheed P-38s, together with four .50 Brownings. It was also installed in nightfighters, which needed maximum firepower to convert a short firing opportunity into a kill. Four were installed in Northrop's P-61 Black Widow, and two could be mounted in a Grumman F6F-5N. The cannon's extra firepower was also appreciated for ground strafing.
After the war the US Navy quickly changed over to the 20 mm cannon in its improved, faster-firing and more reliable M3 form, but the USAF stayed with the .50 M3 until the fighting in Korea demonstrated once and for all that the HMG had had its day. From the mid-1950s the USAF at last replaced the old Browning with 20 mm cannon, initially the M39 revolver and then the M61 rotary - just as most of the rest of the world was moving up to 30 mm!"
Shortround6
Major General
.303 ammo seemed to weigh 6.64lbs per hundred rounds-belted. The links on RCMG ammo aren't too heavy so shouldn't be a big deal. difference in weight of ammo between 300rpg and 350rpg is 26.56lbs.
We do have the answer for the often asked question of why not use four .50 guns on a BoB fighter. for the weight of eight .303s and 350rpg you get four .50 cal guns and 130rpg or just under 10 seconds firing time for 156lbs of ammo. .50 cal ammo is about 30lbs per hundred belted. for 17 seconds of firing time for four .50 cal guns the ammo weight is about 265lbs.
I try not to get to excited about a difference of a few pounds, not all projectiles weighed exactly the same and as noted the guns themselves varied a bit due needed accessories (not including mounts, ammo boxes, heaters, etc). On the Hispano gun the belt feed mechanism was a separate assembly that could be unbolted from the gun, I am not sure if the gun could easily be converted back to drum feed. But this extra "assembly" could help explain the difference between the "nominal" weight of the Hispano and the installed weight.
It is when the weight differences get to the 100-200lb range that things begin to get important.
The P-47 seems to be the champ of WW II single engine fighters with 613kg worth of guns and ammo ( at 425rpg which it did not carry often when hauling large underwing loads?)
Shortround6
Major General
It is true, one of the major differences was the American guns had a chamber that was just a fraction of an inch ( a millimeter or 2) longer than the British guns. This did not provide enough support when the firing pin struck the cap, allowing the cartridge to slide forward cushioning the firing pin strike and causing misfires.
Users who are viewing this thread
Similar threads
