Yanks and their MG's

[David603]

Originally Posted by whatnot

One thing I've found curious the deeper I've gone studying the fighter development from 1930's forwards is that why did the US stick with 50 cals as their weapon of choice on fighters for so long?

I'm no über-guru in the topic, but during WW2 for example the only cannon I find is the hispano in P-38. Then even going to the jet age P-80 and F-86 both had MG's until F-86 H model.

So was it the high rate of fire, smaller weight, logistics of the ammo, the lack of bombers to shoot down or didn't they just get the advantages of a bigger caliber until later?

The simple answer is that the USAAF and USN wanted the 20mm, but US built Hispano cannon were very unreliable. Consequently, they had to stick with .50cals. Given a general lack of bomber opposition, .50cals proved sufficient, and even up until the end of the war US Hispano cannon remained unreliable.

After WWII, the USAAF was quite happy with its .50cals, but the USN still wanted 20mm, and they finally had a reliable version of the Hispano.

Rate of fire between a M2 .50cal and a 20mm Hispano cannon are very close, and most estimates of the firepower of a Hispano cannon give around 3-3.5 times as much power for the same firing time as an M2 MG, so the 4 20mm of a Tempest or Spitfire Mk.21-24 have an equivalent firepower to between 12 and 14 .50cal MGs. Even an E Wing Spitfire with 2x20mm and 2x.50cal has firepower equivalent to 8-9 .50cal MGs.

[whatnot]

Originally Posted by David603

The simple answer is that the USAAF and USN wanted the 20mm, but US built Hispano cannon were very unreliable. Consequently, they had to stick with .50cals. Given a general lack of bomber opposition, .50cals proved sufficient, and even up until the end of the war US Hispano cannon remained unreliable.

After WWII, the USAAF was quite happy with its .50cals, but the USN still wanted 20mm, and they finally had a reliable version of the Hispano.

Wasn't the later Hispano's like Mk V. used in Tempest pretty realiable already? And what kind of failure rates are we talking about with Hispano? Did it jam every 10th belt or what and what made the RAF to go that direction instead of sticking with the MG. So why did it take until mid 50's or whatever to mount them?

And what about the cannons on Russia and Germany used? One would assume that the technology and production blueprints would have been either handed over through reversed lend/lease or captured as the US pushed deeper into germany. Were VYa-23's and ShVAK's just as unrealiable as Hispano's?

[David603]

Originally Posted by whatnot

Wasn't the later Hispano's like Mk V. used in Tempest pretty realiable already? And what kind of failure rates are we talking about with Hispano? Did it jam every 10th belt or what and what made the RAF to go that direction instead of sticking with the MG. So why did it take until mid 50's or whatever to mount them?

And what about the cannons on Russia and Germany used? One would assume that the technology and production blueprints would have been either handed over through reversed lend/lease or captured as the US pushed deeper into germany. Were VYa-23's and ShVAK's just as unrealiable as Hispano's?

The British Hispano was reliable, the RAF had eliminated almost all the problems by the time production moved to the Mk.II, and the Mk.V was very reliable.

The US M1 version was a very different beast, with a high rate of misfires and jamming. The US tried to fix the problems with the M2, but it was equally unreliable. The RAF had been hoping to use US built Hispanos to supplement British produced models, but these proved too unreliable for service introduction.

The problems with US built Hispanos were not solved until after WWII, and in the meanwhile they were only used on aircraft that could mount them in the fuselage, which reduced the problems caused by vibrations and flexing wings, although the misfiring problems remained. Even there they were not very reliable (there is a good reason the P38 had a mixed battery of 4 .50cals and one 20mm).

[K_Freddie]

There was also the 'problem' of using other nations more reliable ammo, and feeding one's own industry (you know, making me[an american at home] rich at the expense of our boys on the front).

[WTE_Galway]

yeah, what everyone else said.

Its not the equivalent of professional motor racing where you go for the technically best possible option regardless of cost. there was a war on and the 0.50 cal was readily avaialble and did the job good enough against fighters.

Add to this the fact that American made 20mm were unreliable in high vibration and flex wing mount positions and too large for "in wing" mounting in existing US aircraft and its clear why they stayed with 0.50 cal.

This link about pattern bore-sight gun harmonization might give you some insight into the some of the issues.

http://www.researcheratlarge.com/Air...nBoresighting/