Yet another .50 vs 20mm thead.

[Shortround6]

There seems to be quite a bit of confusion about the American .50 cal gun/ammo and its effectiveness and efficiency, which are not the same thing.

The .50 cal Browning had a lot of things going for it and many good qualities, however many of these came with a price.

Reliability = Heavy
Durable = Heavy
High velocity = Heavy

The Russian 12.7mm machine gun may have been reliable but it was not durable. The receiver and internal action parts had a life 1/2 to 1/4 that of the Browning. The German MG 131 was about 55% as powerful per round and could be lighter because of that. The Japanese and Italian 12.7mm machine guns were also much less powerful per round. These Axis rounds ( and the British .5 in) used lighter bullets at lower velocities. They could use shorter/lighter barrels and shorter, lighter receivers. Some of these guns could fire faster than the Browning ( and some synchronized much better) but they did not have the penetration power, the smashing power of the American and Soviet 12.7mm guns and they had longer flight times which made deflection shooting harder or shorter ranged ( or both).

The Japanese Navy and the Luftwaffe both used a rather low powered 20mm cannon at the start of the war. Measured by kinetic energy they were about 30% more powerful than the .50 but had the huge advantage of exploding shells. However the guns were slow firing, roughly 2/3rds the cycle rate of the .50 once the .50 got to 750-850rpm, had limited ammo capacity and fired their shells about 2/3rds as fast which again limits the effective range for air to air gunnery. They did weigh about the same, if not a bit lighter, than the .50 Browning though.

Both the Japanese and the Germans introduced newer, more powerful 20mm guns but they gained weight. The Hispano started heavy (designed for durability) but was the most powerful of the common airborne 20mm guns of the war.

Comparing the Hispano to the .50 cal in the air to air role means forgetting a lot of the advantages of the .50 in the ground role. At 600yds at sea level the Hispano shell arrives about 1/10 of a second behind the .50 cal bullet. It takes the .50 cal about .7 seconds to cover the 600yds. At 1000yds the difference has grown to 4/10ths of a second. The .50 does have definite advantage over the Hispano (and every other WW II 20mm aircraft gun) but it doesn't show up vs the Hispano until you are on the fringes of practical air to air ranges, the advantage does show up at more moderate ranges vs the slower 20mm types.

Much is made of the Americans KEEPING the .50 cal not only for the war but till and through the Korean war, at least by the Air Force. That is true but it wasn't for want of trying. The number of projects for faster firing .50 cal guns ( finally bearing fruit in the spring/summer of 1945), higher velocity .50 cal guns ( using several different cartridge cases), .60 cal machine guns ( again with more than one cartridge) and 20mm guns number in the dozens. An awful lot of time, money and effort spent if the US was truly satisfied by the .50 cal Browning. Granted most of projects came to nothing (in part because of too ambitious goals) but does show that the US ordnance officials were not happy with the .50 cal.

 

[fastmongrel]

Unfortunately the .50 v 20mm debate always goes the same way. Mostly US forumites defending the Good Old .50 against the ungodly hordes of cheese eating surrender monkey 20mm cannon. Along the way come claims about how Bombers were chopped in half, Tiger tanks were blown up and Destroyers were sunk by the mighty .50

The .50 was certainly proven to be adequate for the US but if the US had faced heavily armed bombers like other air forces did I believe the 4 or 6 x .50s would have been found similar to the 8 x .303 of the RAF in 1940 adequate but not quite good enough. Just because the US didnt have to face such foes is no excuse all armed forces should look to the worst case scenario and should equip themselves or have available the equipment for this task. The real villains of the peace were the people who were responsible for the shoddy design and manufacture of the US Hispano, if the US had needed the 20mm gun in a rush they would have been in a pickle till they could have got supplies of an adequate weapon. I still find it deeply shocking that the country who came up with so many brilliant easily made weapons could drop the ball so badly with the Hispano. I dont know if anyone went to prison for this debacle but someone should have been tried on charges of treason.

My take on the Browning v Hispano is the Berezin B-20 now that was how to build an aircraft cannon, as light as the Browning with approximately the same ROF and almost the Hispanos power.

 

[ShVAK]

My take on the Browning v Hispano is the Berezin B-20 now that was how to build an aircraft cannon, as light as the Browning with approximately the same ROF and almost the Hispanos power.

And maybe half the longevity, as Shortround noted. That might've been fine for the VVS' purposes but I'd rather have a slightly heavier gun if it meant it didn't burn out in the middle of a dogfight.

 

[fastmongrel]

And maybe half the longevity, as Shortround noted. That might've been fine for the VVS' purposes but I'd rather have a slightly heavier gun if it meant it didn't burn out in the middle of a dogfight.

If the Hispano and Browning had a life of say 10,000 rds then a life of 5,000 rds is fine. How many aircraft guns wore out before the aircraft became a hole in the ground or the armourer pulled it out and replaced it. If the gun wore out during a flight then the armourer should have been reassigned to latrine duty.

 

[Tante Ju]

There seems to be quite a bit of confusion about the American .50 cal gun/ammo and its effectiveness and efficiency, which are not the same thing.

The .50 cal Browning had a lot of things going for it and many good qualities, however many of these came with a price.

Reliability = Heavy
Durable = Heavy
High velocity = Heavy

The Russian 12.7mm machine gun may have been reliable but it was not durable. The receiver and internal action parts had a life 1/2 to 1/4 that of the Browning.

Important for a ground weapon, unimportant for an air weapon. How much was the avarage belting for a .50 cal HB - 300 rounds? What was the loss rate for aircraft, like 5%? That means the gun is lost or destroyed statistically after 20 chances to fully empty its rounds. That's 6000 rounds fired, at best, and much, much less in practice. So why build such a gun that will not survive the aircraft anyway?

Durability of the internal mechanism does not tell much of the service needs of the gun. A gun firing far more powerful rounds will eat up the barrels quickly, and will need replacement more quickly. Worn barrels will degrade muzzle velocity and dispersion, so it would be interesting how did a typical Browning MV looked like after the barell fired 1000 rounds compared to the competetion, and what lifespan (no. of bullets fired before replacement) was claimed for the aircraft mounted version (not the HB version). I would risk a bet that the difference wasn't very great anymore.

For the American .50 cal heavy machine gun, the manual stated no more than 75 rounds to be fired in one burst, and that has to be followed after one minute of cease firing by one 25 round burst per minute. The gun was to be cooled for at least 15 minutes before another long burst was attempted. I am sure pilots and gunners were less concerned about that when enemy aircraft were around, but it was at the expense of exponentially increased wear on the barrel and internal parts, giving a proper context to those rather theoretical figures you quoted.

The German MG 131 was about 55% as powerful per round and could be lighter because of that. The Japanese and Italian 12.7mm machine guns were also much less powerful per round. These Axis rounds ( and the British .5 in) used lighter bullets at lower velocities. They could use shorter/lighter barrels and shorter, lighter receivers. Some of these guns could fire faster than the Browning ( and some synchronized much better) but they did not have the penetration power, the smashing power of the American and Soviet 12.7mm guns and they had longer flight times which made deflection shooting harder or shorter ranged ( or both).

"Smashing power" is an interesting concept. I guess it was created very recently to get something. Unfortunately such smashing power doesn't exist for aircraft - be it the Russian UBS, the German Mauser or the American Browning, they all just made roughly 13 mm holes in aluminium skin that was no more than 1 mm thick typical, and all could penetrate armor on aircraft reliably, pierce fuel tanks and radiators, "smash" radios and generators. It didn't not matter much in the air if the Browning could penetrate as much as (let's say) 25 mm of steel armor and the other only 15mm if all that was to be found on aircraft was 4-8mm.. That was all that was to be asked from an aircraft gun IMHO, and others seem to have correctly realized that anything else is an overkill and adds nothing of practical value, but results in a heavier gun.

The Japanese Navy and the Luftwaffe both used a rather low powered 20mm cannon at the start of the war. Measured by kinetic energy they were about 30% more powerful than the .50 but had the huge advantage of exploding shells. However the guns were slow firing, roughly 2/3rds the cycle rate of the .50 once the .50 got to 750-850rpm, had limited ammo capacity and fired their shells about 2/3rds as fast which again limits the effective range for air to air gunnery. They did weigh about the same, if not a bit lighter, than the .50 Browning though.

When was the cyclic rate of the M2 Browning improved to 750-850? Shwak cannon production started in around 1936, Mauser MG 151/15 version in 1938... the Oerlikon FF goes back to WW1, but it was fitted to LW aircraft since 1937 on trials.

Both the Japanese and the Germans introduced newer, more powerful 20mm guns but they gained weight. The Hispano started heavy (designed for durability) but was the most powerful of the common airborne 20mm guns of the war.

"Heavy" does not equal durability outside the US.. the Hispano in fact was very slim, what made it heavy was it's very long barrel made for it's powerful round. It's a distant relative to the Oerlikon cannons anyway (which existed if utterly powerful forms, though usually the 'compact' FF version was picked for aircraft by most and is best known).

Comparing the Hispano to the .50 cal in the air to air role means forgetting a lot of the advantages of the .50 in the ground role. At 600yds at sea level the Hispano shell arrives about 1/10 of a second behind the .50 cal bullet. It takes the .50 cal about .7 seconds to cover the 600yds. At 1000yds the difference has grown to 4/10ths of a second. The .50 does have definite advantage over the Hispano (and every other WW II 20mm aircraft gun) but it doesn't show up vs the Hispano until you are on the fringes of practical air to air ranges, the advantage does show up at more moderate ranges vs the slower 20mm types.

600 and 1000 yards are completely unrealistic for aircraft mounted guns for any kind of aimed fire. Not only it was humanly extremely difficult to even see much less aim at a target that far from an aircraft, but the dispersion of the gun was such that even with perfect aiming marginal number of hits would obtained anyway. Sure many rounds can be fired from many Brownings - by which time you are probably at the same weight and bulk as simply fitting a gun with truely impressive ballistic potential like the Mk 103.

 

[Xjrtaz]

Now this is quite an interesting topic.
As far as the British .303, that is altogether another forum topic, all I can do is quote what my father stated about his experience with the armament on the Hurricane and Spitfire, compared to the .5's on his Thunderbolt.
My father is Witold `Lanny' Lanowski, Polish fighter pilot with a wealth of experience before he joined the 56th FG. he always said and I quote (baring in mind that you have to imagine a twang of a polish accent here) "bloody pop guns" He hated them with a passion, he prefered that they were situated side by side on the Hurricane giving you at least some concentrated firepower, but the Spit?...well, he detested it, so many faults, fataly proved by one Polish pilot to the Aero engineers from farnborough whilst stationed with 302 SQ at Northolt, one of them being fitted with a rifle caliber bullet, located spaced innefectually apart on the wings (not designed to carry weapons!!). The polish pilots zeroed thier 303's to 100yds as as my father said, "you needed to get right up the Niemcy's ass!" to hope to do any lasting and immediate damage.
When he flew Thunderbolts (and the Mustang with the 354th) he was overwhelmed by the destructive power of the .5. one of his combat reports states that a half second burst and the 190 disintegrated in front of him...!
I also remeber my father commenting on being fired at by 20mm cannons, he said it was a frightening experience if they hit you, but thier ROF was much slower then that the mg's that were also fitted to the German fighters
I hope this sheds some light from a fighter pilots point of view

 

[CobberKane]

If the Hispano and Browning had a life of say 10,000 rds then a life of 5,000 rds is fine. How many aircraft guns wore out before the aircraft became a hole in the ground or the armourer pulled it out and replaced it. If the gun wore out during a flight then the armourer should have been reassigned to latrine duty.

All depends on the circumstances, I guess. No doubt the AVG were very happy to have the extended life of the Browning, given how long their supply ines were. The Soviet doctine of quantity over quality also makes sense, if you have secure supply lines to a large industrial base and pleny of manpower to expend. What was it Stalin said? "Quantity is its own quality."
I think its important to remembr that US fighters never really met anything bigger than medium bombers, and throughought the ETO escort role even those were really targets of opportunity. Bomber interception in the ETO, where most of the resources went, was a secondary consideration for American fighters; for most of the time the main job was to knock down single and twin engine fighters. For this purpose the .50 was effective, available and proven. Doubtless the USAAF recognised its limitations in roles beyiond that in which they were typically using it, and maybe by the time of Korea they should have gone the Navy way and got the cannon right, but it certainly got the job done during WWII.

 

[wuzak]

Also, wasn't the 37mm cannon the USAAF's preferred weapon for bomber interceptors?

The XP-67 was designed as a long range bomber interceptor, and was to have 6 x 37mm cannon!

 

[Shortround6]

An Attempt to address some of the issues brought up.

"My take on the Browning v Hispano is the Berezin B-20 now that was how to build an aircraft cannon, as light as the Browning with approximately the same ROF and almost the Hispanos power"

The Berezin B-20 didn't show up until some point in 1944 and wasn't in wide spread use until 1945 ( and wide spread was still a far cry from universal)

"If the Hispano and Browning had a life of say 10,000 rds then a life of 5,000 rds is fine."

It might have been fine but most of the Russian guns were closer to a 2500 round life. It suited the Russian style, it suited the Russian problem of low powered engines and it suited the Russian supply situation. Replacement guns did not have to come by ship and take weeks if not months to get to the front.

I specifically said receivers and internal parts because barrels were a consumable item and were expected to be changed several times (at least) before the receiver and lock work wore out. This goes for most peoples aircraft guns. A decently equipped armourer would have a throat gauge or inspection tool and replace barrels before wear got to be too big a problem. Remote air fields and supply problems in a particular theater/time period obviously affect things.

"Unfortunately such smashing power doesn't exist for aircraft...."

Actually it does. Please find an aircraft that was of "pure" monocoque construction. Despite descriptions saying an aircraft was of monocoque construction just about all aircraft were of semi-monocoque construction. They used spars and ribs in the wings and sometimes stringers, They used longerons, frames and/or bulkheads and stringers in the fuselage. They used motor mounts to fasten the engine to the airframe and used mounting plates or flanges at times for the motor mounts or wing to fuselage joints ( or tail planes). It was the ability of the large caliber weapons to break or seriously damage/degrade these structural components that caused aircraft to break up in the air. Granted it was a minority of the projectiles that hit an aircraft that hit structural components. It was also found that the Heavy Machine guns and cannon firing "ball" ammo (non-exploding) could, on occasions, split nearly full fuel tanks open along the seams rather than just punch holes in them. It depended on the size of the tank, the % of fuel in the tank, if the bullet hit well below the top of the fuel level or went over it and so on but the effect was there and could not be accomplished in aircraft sized fuel tanks with rifle caliber machine guns.

I am not sure what phrase or word describes splitting open fuel tanks, breaking engine mounts, or causing wing spars/wing to fuselage joints to fail but "smashing power" works for me. Against the .50 is the fact that the British 20mm Hispano "ball" round was even better at these things.

"When was the cyclic rate of the M2 Browning improved to 750-850? Shwak cannon production started in around 1936, Mauser MG 151/15 version in 1938... the Oerlikon FF goes back to WW1, but it was fitted to LW aircraft since 1937 on trials."

The M2 Browning was upgraded in 1940. I don't know if existing guns could be upgraded with new parts or not. The 1945 switch to the 1200rpm M3 required new guns, M2s could not be retro fitted. If the Germans were really in production of the MG 151/15 in 1938 it sure took them a long time to fit them to service aircraft in large numbers. I know they were used in the Spanish civil war in trial quantities (less than a dozen?) They don't seem to reappear until 1940, again in small quantities and finally make it into a fighter at the end of 1940/beginning of 1941. The Oerlikon FF does NOT go back to WW I. It can trace it's ancestry back to WW I which is a bit different. The WW I Becker cannon used somewhat less powerful ammunition, was heavier, and fired at around 300rpm. It was developed into the Oerlikon F which was developed into the Oerlikon FF.

I am trying for the balanced look and in many other threads I have been critical of the .50 Browning. It is certainly not the supergun that many make it out to be but it is also one of the 3 most powerful commonly used machine guns in WW II ( this depends on how you class the MG 151/15) and it's margin of power over over the German 13mm and Japanese/Italian 12.7 was substantial. It's time of flight offered an advantage over some of the lower powered 20mm guns in terms of hit potential as did it's higher rate of fire. Those are facts that cannot be wished away. On the other hand the .50 offered no practical advantage in time of flight compared to the Hispano over normal air to air ranges, and some of the later axis 20mm guns, the Soviet 20mm guns and the last Hispanos gave it a run for it's money in terms of rate of fire.

 

[CobberKane]

Gidday, Wuzak - watch the game? You almost had me eating crow over those radial engines...

One other thing we can thank the .50s for is the camera footage they left us. None of this 'two hits and he's aluminium dust' crap you get with Hawker Tempest footage; lots of little flashes, bits falling off, pilot bailing - way more cool!

 

[Shortround6]

Also, wasn't the 37mm cannon the USAAF's preferred weapon for bomber interceptors?

The XP-67 was designed as a long range bomber interceptor, and was to have 6 x 37mm cannon!

The US had some rather bizarre notions as to what constituted bomber interceptor armament. Of course having built the XB-15, The XB-19, working on the B-29 and "The USAAC opened up a design competition for the very long-range bomber on 11 April 1941" and placing the contract for 100 B-36s on 23 July 1943 maybe they had an idea of what it would take to shoot down truly big bombers?

I like the XP-54 with two 37mm and two .50 cals with the .50 cal guns fixed but the 37mm in a tilting nose section so that they could get common points of impact at different ranges

 

[wuzak]

Gidday, Wuzak - watch the game? You almost had me eating crow over those radial engines...

No, I did not.

 

[CobberKane]

No, I did not.

19 all at full time. All Blacks took a penalty scrum afte the whistle and played on for five more minute before finally missing a dop goal

 

[davparlr]

Doubtless the USAAF recognised its limitations in roles beyiond that in which they were typically using it, and maybe by the time of Korea they should have gone the Navy way and got the cannon right, but it certainly got the job done during WWII.

At the time of the Korean War the Navy F9F was using four slow firing and apparently problematic M-3 Cannon whereas the AF F-86 was using six very fast firing M-3 machine guns. My analysis on probability of hit verses effectiveness of projectile indicated that, for two to three second burst, both packages are comparable in effectiveness, with the F9F having an advantage at long ranges but the F-86 was more effective at closer combat.

According to wikipedia (?) the Navy continued to have problems with its 20mm cannons through Vietnam. However, for early 50's, the AF got the better gun when they upgraded the M-3 machine guns on the F-86H, and on, to the vastly superior (as compared to the .50s), and faster firing, M-39 cannon.

 

[gjs238]

What do the P-38 pilots say about it?
When/how did they use the 20mm vs the .50?
What results were achieved?

 

[gjs238]

The 20MM was installed on a US heavy bomber.
Don't know how often this was done.
I think it was an unofficial field mod.
I remember reading about vibration/mount issues.

 

[VBF-13]

The polish pilots zeroed thier 303's to 100yds as as my father said, "you needed to get right up the Niemcy's ass!" to hope to do any lasting and immediate damage.

That's the shortest I think I've ever heard. Your Dad was right, that's close company. I could be mistaken about this, but I believe my Dad's Hellcat was zeroed at 300 yards.

When he flew Thunderbolts (and the Mustang with the 354th) he was overwhelmed by the destructive power of the .5. one of his combat reports states that a half second burst and the 190 disintegrated in front of him...!

I can definitely believe that.

 

[oldcrowcv63]

Didn't the Geneva Convention "outlaw" or in some fashion proscribe the quad 0.50" as an inhumane weapon? I have to wonder just how humane would be a quad 20 mm.

 

[davparlr]

The polish pilots zeroed thier 303's to 100yds as as my father said, "you needed to get right up the Niemcy's ass!" to hope to do any lasting and immediate damage.
When he flew Thunderbolts (and the Mustang with the 354th) he was overwhelmed by the destructive power of the .5. one of his combat reports states that a half second burst and the 190 disintegrated in front of him...!

At 100 yds it is probably hard to miss. A half second focused burst from a P-47, about 40 or so rounds, at a hundred yards, would have a devastating effect on any airframe.

 

[CobberKane]

What do the P-38 pilots say about it?
When/how did they use the 20mm vs the .50?
What results were achieved?

That's a good question. I suspect the ballistics of the Hispano were less dissimilar to an HMG than was the case with the heavier cannon used on some other types. I don't think the 37mm on the P39 had too many fans amongst US pilots; I read a few accounts of them preferring the P400, or just not using the 37mm even when it was avaialable.