Why was the US the only nation to rely on the 50

[DerAdlerIstGelandet]

Seriously though, the Genev Conventions does not prohbit the use of the .50 BMG on people. Just because the military has a policy doesn't mean that policy is rooted in the Geneva convention. American snipers have been using the .50 against persons for years now. Look at this link . (Do not open it if you are not prepared for a very graphic image.)

http://poetry.rotten.com/failed-mission/failed-mission.jpg

Use of heavy caliber machine guns aganst troops, whether from a sniper rifle, atop a tank or on fighter aitrcraft, has never shocked the conscience of the combatants in war.

You are more than likely correct. I can not quote a paragraph or page or anything. It is more than likely not an actual law. It is however during our Geneva Convention training pretty much stated in our policy on the .50 Cal. Now as you said Snipers do use the .50 Cal and yes in an actual combat situation I would have no problem using a .50 Cal on people.

 

[Magister]

Thanks to that .50, it looks like that insurgent finally got his one way ticket to see Allah.

 

[MacArther]

yes, he probably though, "I will do this for mySPLAT"

 

[DerAdlerIstGelandet]

We need to see more like that.

 

[Glider]

Sources checked.
Initial tests were undertaken in the 1920's as it was recognised that 2 x LMG wouldn't be sufficient for long. Guns used were the Browning and Vickers 0.50 calibre and the Oerlikon 20mm Type S but no decision was made.
In the mid 30's aircraft had made significant improvements and it was recognised that the 303 was to small. In 1936 the French demonstrated the HS404 in Paris tests were undertaken and this was chosen for the RAF. An RAF ACAS report of 1938 stated that every effort should be made to ensure rapid production. In the meantime the decision was taken to increase the firepower of the latest planes (read Hurricane and Spitfire) to 8 x LMG. Its worth mentioning here that the Spitfire was originally designed for 4 x LMG and amended to 8 X LMG. Its one of the differences between a Spit 1 and a Spit 1a.

As outlined above the British did have 0.50 MG's in production, the Vickers which was developed into a quad mount AA gun for the Navy. We didn't have a 20mm in production. The Masden was the other 20mm that was compared to the HS404 in the 1936 tests.

Re the guns on USA Aircraft I think you will find that the first P40's only had LMG's, the P36 had LMG's and the P43 Lancer had 2xHMG and 2 x LMG. So even in the USA there was a certain amount of uncertainty.

We didn't need the help of the USA in mass producing the DeWilde ammunition technically. We had a shortage of production capacity across the board and this may have been the cause of some confusion.

The USA 20mm was definately based on the original French weapon. We were almost begging the USA to use our specs as we wanted to use these guns in our aircraft. In the end the USA provided thousands of 20mm to the UK under lend lease and we didn't mount a single one on an RAF aircraft.
The major and most significant difference was the size of the chamber. I am afraid that you have it the wrong way around it was the UK chamber that was 1/16th of an inch shorter and its the one things the USA refused to change. As a result the largest cause of jams, soft striking continued in the US weapon and was rare in the UK weapon. The British observers noted and commented on the quality of finish of the USA weapons as being much higher than that of the UK gun.

P51B guns were noted for their unreliability. The feed was awkward, the gun was mounted on an angle and it often jammed. I don't know if adding a nickle would have helped reliability, rof maybe but reliability I doubt. Do you know if they used the nickle on the P51D, Hellcat, P47 or anything else that used the .50 or was it just for the P51B?

I believe that your view of the .50 against a heavy bomber are flawed. Everyone who took on these aircraft upgunned preferably to 30mm. To believe that the 12.7 would do as well or even close to as well is in my view, very, very, optimistic. Me I would go with 4 x 20.

The fusing problems of the 20mm was a real problem early in their deployment. For that reason a number of RAF squadrons originally used all AP as it would do a lot of damage to whatever it hit but this was solved by 1942 when our fused would go off a fraction of a second after hitting the plane doing the most damage.

As for your comment on reliability my second post which presumably crossed covered that point but the results for the British gun would have been a lot better if the ammo hadn't been greased. If our's were bad the USA ones were awfull.

Spit 9's always had either 2 x 20 plus 4 x LMG or 2 x 20 plus 2 x HMG not just 2 x 20. As for firing the sign of an experienced pilot was using one gun to find the range and then letting fly but this was very rare. Nearly all pilots in all airforces would let fly with everything they had if an enemy was in front of them as tragically it was often the only chance they had.

The only UK fighter I have found that flew with only 2 x 20 were Hurricane IIc's, which sometimes had two of the guns taken out to improve performance over Malta.

Re Rate of Fire. The quoted one is normally 600rpm for the 20mm. The RAF Manual said 650, the test of a Beaufighter was 700 and the test of another plane was 530. None of these firures suprise me as mass production could make them vary by 10-15% of base figure. If you average them you get 620 which is so close to the 600 its not worth arguing about. If you cannot hit the plane with 600 rpm I doubt if you could hit it with 620.
Personally I would like 2 of those Molins guns please. Then I would happily leave my 4 x LMG or 2 x HMG behind and carry extra ammo.

 

[CharlesBronson]

Wow, good discussion so far. How about the Japanese 13mm? I think it was only on one torpedo plane that had to be used from land bases because there were no carriers left by the time it entered service. On a side note, I would hate to be a Japanese armorer, imagine trying to get all the different amunition types, and making sure they were rimmed or unrimmed!

The navy used two types of 13 mm Mg, one was the 13,2 Japanese Navy Type 3 13,2mm (13,2x99) rimless derivated from a French Hochtkiss cartrigde but in a Browning M2 gun, that was used in the Mitsubishi A6M5.

The other 13mm was the Type 2, a copy of the german Mg-131, it was emplaced as defensive armament in the late torpedo -bombers.

 

[Lunatic]

Sources checked.
Initial tests were undertaken in the 1920's as it was recognised that 2 x LMG wouldn't be sufficient for long. Guns used were the Browning and Vickers 0.50 calibre and the Oerlikon 20mm Type S but no decision was made.
In the mid 30's aircraft had made significant improvements and it was recognised that the 303 was to small. In 1936 the French demonstrated the HS404 in Paris tests were undertaken and this was chosen for the RAF. An RAF ACAS report of 1938 stated that every effort should be made to ensure rapid production. In the meantime the decision was taken to increase the firepower of the latest planes (read Hurricane and Spitfire) to 8 x LMG. Its worth mentioning here that the Spitfire was originally designed for 4 x LMG and amended to 8 X LMG. Its one of the differences between a Spit 1 and a Spit 1a.

As outlined above the British did have 0.50 MG's in production, the Vickers which was developed into a quad mount AA gun for the Navy. We didn't have a 20mm in production. The Masden was the other 20mm that was compared to the HS404 in the 1936 tests.

The Vickers was not suitable for a variety of reasons. Amount them I believe were the way the ammo feed worked, and the max RoF was too slow. It would have required a complete re-design. Ammo production was quite limited too.

Re the guns on USA Aircraft I think you will find that the first P40's only had LMG's, the P36 had LMG's and the P43 Lancer had 2xHMG and 2 x LMG. So even in the USA there was a certain amount of uncertainty.

While the British were looking at the Hispano in the years immediately prior to the war, they did not get serious about it until the war had already started. My point is the USA had by this time already made a commitment to the .50, I believe in 1932 or so.

The USA 20mm was definately based on the original French weapon. We were almost begging the USA to use our specs as we wanted to use these guns in our aircraft. In the end the USA provided thousands of 20mm to the UK under lend lease and we didn't mount a single one on an RAF aircraft.

The major and most significant difference was the size of the chamber. I am afraid that you have it the wrong way around it was the UK chamber that was 1/16th of an inch shorter and its the one things the USA refused to change. As a result the largest cause of jams, soft striking continued in the US weapon and was rare in the UK weapon. The British observers noted and commented on the quality of finish of the USA weapons as being much higher than that of the UK gun.

No I had it right. The original spec called for a longer chamber, and the USA built their guns this way and it took a long time for them to adjust it as the British suggested AFTER THEY PROVIDED DRAWINGS SHOWING THE LONGER CHAMBER DESIGN. The US Hispano was based upon British drawings which had to be redrawn to US production specs.

P51B guns were noted for their unreliability. The feed was awkward, the gun was mounted on an angle and it often jammed. I don't know if adding a nickle would have helped reliability, rof maybe but reliability I doubt. Do you know if they used the nickle on the P51D, Hellcat, P47 or anything else that used the .50 or was it just for the P51B?

The problems on the P-51B are well noted. However, these problems were almost totally solved within months of the planes deployement through the use of a feed motor scavenged from the Marauder. Once the feed motor was installed the problems were virtually solved - a point that seems to be generally missed. The nickle did not hurt reliabilty much, but it did wear out the gun quite a bit quicker. However, there was no shortage of replacement .50's in the ETO.

I believe that your view of the .50 against a heavy bomber are flawed. Everyone who took on these aircraft upgunned preferably to 30mm. To believe that the 12.7 would do as well or even close to as well is in my view, very, very, optimistic. Me I would go with 4 x 20.

And none of them mounted EIGHT .50 class guns. I'd probably choose 4 x Hispano's too, but only if I had 200 rpg or more.

The fusing problems of the 20mm was a real problem early in their deployment. For that reason a number of RAF squadrons originally used all AP as it would do a lot of damage to whatever it hit but this was solved by 1942 when our fused would go off a fraction of a second after hitting the plane doing the most damage.

Actually, a lot of BALL ammo was used by the RAF through 1943. It was not until late 1943 that the superior fused rounds reached the front in significant quantities.

As for your comment on reliability my second post which presumably crossed covered that point but the results for the British gun would have been a lot better if the ammo hadn't been greased. If our's were bad the USA ones were awfull.

Perhaps. But the jam rate figures I quoted were 1:1500 for the Hispano, which A LOT BETTER right? It is still quite a bit less reliabiable than that of the .50's, which were something like 1:6000 by the end of the war. And given the larger number of guns and ammo supply, and the ability of a .50 to be fired even if it's mate was jammed where the 20mm could not do this, the jam issue is even more signficant.[/quote]

Spit 9's always had either 2 x 20 plus 4 x LMG or 2 x 20 plus 2 x HMG not just 2 x 20. As for firing the sign of an experienced pilot was using one gun to find the range and then letting fly but this was very rare. Nearly all pilots in all airforces would let fly with everything they had if an enemy was in front of them as tragically it was often the only chance they had.

If you check pilot accounts you will find that this is not true. Most Spit IXc's had 2 of the cannon removed. This allowed more ammo to be loaded in the remaining 2 cannon, and improved the planes performance. Also, the position of the two cannon removed was much more prone to jamming because of the ammo feed.

The only UK fighter I have found that flew with only 2 x 20 were Hurricane IIc's, which sometimes had two of the guns taken out to improve performance over Malta.

The same was done with the Spit IXc. This was why on later model Spit IX's and XIV the armament was changed back to two 20mm's plus 2 x .50's or 4 x .303's. The issues with the 4 x 20mm setup were not resoved until the Spit Mk.20's came online in 1945.

Re Rate of Fire. The quoted one is normally 600rpm for the 20mm. The RAF Manual said 650, the test of a Beaufighter was 700 and the test of another plane was 530. None of these firures suprise me as mass production could make them vary by 10-15% of base figure. If you average them you get 620 which is so close to the 600 its not worth arguing about. If you cannot hit the plane with 600 rpm I doubt if you could hit it with 620.
Personally I would like 2 of those Molins guns please. Then I would happily leave my 4 x LMG or 2 x HMG behind and carry extra ammo.

Well I've seen all kinds of figures thrown about. But actuall tests of in-service aircraft always show RoF's below 600 rpm. When I go home in late January I'll try to find the German test data. However, I'm not disputing the 600 rpm figure for the Hispano, just stating that it is near the maximum. For the .50, 800 rpm seems the reasonable figure to use since the guns came from the factory rated at 750-850 rpm, adjustable by how the headspacing was set, on a new gun.

With the 57mm molins gun you'd be toothless vs. any fighter. It doesn't matter how big the round is if it fails to hit the target.

=S=

Lunatic

 

[Glider]

Lunatic
The first American 20mm was based on the original French Birkigt type 404 and was known as the American M1 and it was this that the USA first manufactured with all the reliability quirks we agree on.
Whilst this was going on the UK which started with the same weapon had developed it into a new version which we called the Mark 2. There were seven main differences between the USA M1 and the UK Mark 2, the main one being the size of the Chamber.
The designs were sent over to the USA in January 1942 with a copy of the improved weapon. The UK was not suprisingly asking for production to be standardised on one model, our Mark 2 as it was far more reliable. Tests were undertaken at Aberdeen, Eglin Field, Wright Field and Kenvil proving ground to test the British suggestions.

It was agreed on 4th April that further tests be undertaken which were the ones I documented in my posting showing the 5000 round test. Despite these results the US Ordnance Department refused to modify the design of USA built 20mm with regard to the chamber. They even refused to let any USA manufacturer build them to UK standards for use by UK forces.
Heaven only knows why they could come up with such a suggestion when the results were as clear as they were.

The point is that the USA had a 20mm based on the HS404 before the British plans arrived for the modified Mark 2 in January 1942.

 

[Glider]

Moving on as my cat just jumped on the keyboard and wiped the rest of the message.
The P51B never really resolved all its problems as one of the main ones was the flexing of the wings under combat conditions could flex and jam the ammo feeds. The motor helped but didn't resolve all the problems.

The 1 in 1,500 is of course a better figure, but be fair, I was only correcting a mistake that I made. No one is saying that the 20mm was more reliable than the .50 just that it was reliable enough.

Spit 9c's carried the 4 x LMG as well as the 2 x 20. The type 9e carried the 2 x HMG instead of the 4 x LMG of that I am certain.
You may be getting confused with the type C wing that could carry 4 x 20 but which never did on a Mk 9. The only Spit I know that carried the 4 x 20 in WW2 were a few Spit 5C in 1944 in Europe. This was because they were used for GA work and were the last few in service as the Mk 9 and others were replacing them. The extra 20 mm came in useful against ground targets.
No Spitfire 9's had Cannon removed to improve performance with the exception of a couple of one off's that had as much weight removed as possible including armour, to reach very high altitude German Recce planes.

Rate of fire I have no objection to people settling for 800 rpm its not that much more than 750 which is normally quoted, they can very significantly
from gun to gun and its not as if anyone is claiming a massive increase.

Lastly. The Molins I was refering to, was the tweeked Hispano II that I mentioned in the posting with the test results that fired at 1000 rounds per minute. A Spit with 2 x 57 would be lucky to get off the ground even if they could be fitted.

 

[Lunatic]

Some 9c's were outfitted with the "C" armanent - 4 x 20mm's. However, most of the time 2 of the 20mm's were removed in the field as I described above. Check it out some, you will see this was the case.

As for the "DeWilde" ammo being of British orign - does it not seem strange to you that this was a "new" ammo type in 1940 but that IM11 based ammo for the US .50 had been in production for over 5 years? To produce IM11 you need to compress the powdered constituants - 25% Aluminum, 25% Magnesium, and 50% Barium nitrate, to almost the inginition point. To do this successfuly requires the use of an inert gas to prevent undesired ignition at a lower compression level, and a refrigerated environment.

The availability of IM11 was another reason the US felt comfortable with the .50. No other nation (except Britain) was able to produce this kind of incendiary. Germany, the Soviets, and the Japanese all tried. Also, IM11 is relatively light compared to HE, so the wieght in grams is decieving. The volume and the heat generated (4000F) is what is important .

IM11 and IM23 incediaries are self-igniting. They burst upon the second metal surface contacted, which generally maximizes the chances of starting a fire within the target.

=S=

Lunatic

 

[Glider]

Lunatic. For the UK forces the new DeWilde ammunition was a total British development and the person who led the investigation and design was one Major Dixon.
We also developed a round for the Vickers .50 for use on ships based on the design of the 303 DeWilde called the Mk B 1z Incendiary which was cleared for use in 1939.
Still looking for the 4 x 20 Mk 9. Can I ask if you could give me some guidance. I would like to identify the Squadron as I do a fair amount of wargames and would like to use it. However will need to support my request.

 

[Lunatic]

I believe some 4 cannon IX's flew with the RAF out of malta, alongside the V's. In both cases the armament was reduced to 2 x 20mm cannon.

Also, the RCAF squadrons 421, and other 400 series squadron's flew them (armed with 4 x 20mm) at Normandy, primarily for ground attack.

=S=

Lunatic

PS: Notice no machine gun ports on the pics below

 

[Jabberwocky]

Don't know about the second picture, but the first one appears to be a LF Mk IXe, not a MK IXc.

Couple of give aways;

1. The longer tropical style nose filter; late production (mid 1943). Not fitted to eariler F MK IX

2. Pointed tail; late production (late 1943)

3. Clipped wings; exclusively used on LF Mk IXc and IXe, again late production

4. Short Hispano cannon barrel (the real clincher); only used on type E wings. The type B and C wings have a longer and more narrow barrel covers, with a straight inital protsions then a long tapering nose with a longer exposed cannon tip. The E type cannon covers are shorter and fatter.

So, its probably a Mk IXe, with a .50cal mounted just inboard of the 20mm cannon.

 

[Lunatic]

Don't know about the second picture, but the first one appears to be a LF Mk IXe, not a MK IXc.

Couple of give aways;

1. The longer tropical style nose filter; late production (mid 1943). Not fitted to eariler F MK IX

2. Pointed tail; late production (late 1943)

3. Clipped wings; exclusively used on LF Mk IXc and IXe, again late production

4. Short Hispano cannon barrel (the real clincher); only used on type E wings. The type B and C wings have a longer and more narrow barrel covers, with a straight inital protsions then a long tapering nose with a longer exposed cannon tip. The E type cannon covers are shorter and fatter.

So, its probably a Mk IXe, with a .50cal mounted just inboard of the 20mm cannon.

????

It's got a 20mm inboard and a capped 20mm emplacement outboard.

 

[Richard_H]

Check your sources. Britian didn't get serious about replacing the .303 until 1940. Experiance showed them 8 x .303's were not sufficient.



The British had no suitable .50 class gun in production. They did have several 20mm's in production of which several were considered and the Hispano was finally chosen. I am quite certain that had the British had a .50 class gun ready to field and facilities for ammo production in 1940 they'd have used it. Since they didn't, they didn't.



All US fighters ordered for the USAAF and USN from 1937 on mounted .50 class guns.



The assistance was in how to mass produce it.



The US Hispano was based upon British specs, not French specs. However, the drawings had to be converted to US standards. Unfortunately, some idiot decided that, being a "cannon", the tolerances should be artillary grade, not machine-gun grade, and so the cannons were not very well built. Also the original British specs called for a chamber that was too long - the firing pin would fail to strike the primer hard enough to fire it. These problems was eventually resolved but led to long delays because, amoung other things, the 20mm was not a high priority and did not recieve the kind of funding other weapons systems recieved, nor the best engineers.



Blow back designs tend to increase in RoF when the springs weaken with use. Gas operated guns tend to decreace in RoF as the works get gummed up and the seals become less and less effective.

The only plane for which 750 rpm is quoted is the P-47, at 100 rps. The P-51D, F4U, Hellcat are all quoted at 80 rps from the factory.

80 rps / 6 = 13.333 ; 13.333 x 60 = 800

So 800 rpms is the reasonable figure to use if factory RoF's are to be used. However, in reality the gun fired faster by the time it reached combat.



The "nickel trick" was the norm for P-51B's in both the 8th and 9th airforce. Armorers and pilots were known to write home asking for nickels for this purpose.



Where did I say "easier"?

But, the P-47 does have several advantages. The .50's can be triggered longer than the MG151/20's, giving more chance to slice at the wings. The .50's also have substantially longer effective range. For this kind of target, the .50's would be effective out to over 500 meters, where the MG151/20's were effective to only a little over half that range. Finally, the P-47 has a volume of fire advantage - 100 rps vs. 41 rps.



But cutting it in half is all that is needed to down a B-17. Blowing it up doesn't make it any deader.

Also, fusing issues were a real problem for the WWII 20mm. Too often the 20mm would burst on the skin and fail to do any structural damage.



The official jam rate for the British Hispano II was 1:1500 rounds fired during the last 12 months of WWII. For the .50 BMG, it was 1:4000 rounds fired measured in 1942 when the USA entered the war. Steralite lined barrels were introduced in 1943-44, decreasing jam rates.

As I recall, in that particular test the British Hispano suffered about 20 jams in 5000 rounds fired - less than 25% that of US Hispano's tested. Still, 20:5000 is... 1 in 250 !

There are many accounts of Hurc IIc's and Spitfires where all the cannon jammed in a single sortie.



The Spit IXc typically flew with 2 x Hispano II's and no mg's. It was a hypothetical comparison anyway.

Besides, the .50's were not generally fired with the Hisapno's - it was one or the other since the trajectories were significantly different.

=S=

Lunatic

The Spit IXc Didn't fly without guns, it either flew with 2x Hispano 20mms and 4 x .303 Brownings or 20 x 20mms and 2x .50 cals brownings.

An earlier mark, Mark V (not Va as it was only equipped with guns) but Mk. VB (2 cannons, 4 guns) and VC (4 cannons) often flew with only cannons.
At least i know that the Spit Mk Vc with 4 cannons tended to only fly with 2 because it weighed a lot more with 4 cannons

 

[Glider]

The Spit IXc Didn't fly without guns, it either flew with 2x Hispano 20mms and 4 x .303 Brownings or 20 x 20mms and 2x .50 cals brownings.

An earlier mark, Mark V (not Va as it was only equipped with guns) but Mk. VB (2 cannons, 4 guns) and VC (4 cannons) often flew with only cannons.
At least i know that the Spit Mk Vc with 4 cannons tended to only fly with 2 because it weighed a lot more with 4 cannons

To a degree I believe you to be correct but I have little doubt that some changes were made in the field.

For instance, the 303 was of little if any good against German Aircraft. If you accept this, then there is no reason why you shouldn't take them out as they are simply dead weight. I am not saying this was common particually late in the war when GA was often the mission, but it wouldn't suprise me if some pilots had them removed.

 

[Tony Williams]

To return to the original subject, this article examines the US choice of fighter armament: CANNON OR MACHINE GUN

Tony Williams: Military gun and ammunition website and discussion forum

 

[Twitch]

This has been discussed in so many other later topics why did this guy revive an 8 month old thread?

 

[the lancaster kicks ass]

newbe.......

 

[MacArther]

Maybe he's a n00b, or maybe....HE LIKES MY POSTS!! HE REALLY DOES!!! YAYYYY