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).

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).

;)

If I had a P38 id ditch all the 50cals and put in like 4 20mms and pack in as much ammo as possible...also make them so they fire alternate instead of all at once so I get better coverage of my rounds...in Il2 the cannons fire slow and the target plane flies between the volleys of cannon shells. The 50 cal is a nice weapon it has good punch and good RoF and all but hte 20mm is just better :cool:

4 centreline mounted 20mm cannon would pack one hell of a punch, and the Hispano Mk.V is only marginally heavier and bulkier than an M2, so replacing 4 M2s with 3 Hispanos would actually result in a weight reduction, though the heavier 20mm ammunition would mean a slight overall increase in loaded weight. The size of the P38's nose would also allow for a lot of ammo, maybe even 250-300 rpg. The Hispano Mk.V has an almost identical rate of fire to an M2, but the alternating fire would still be useful.

Imagine a P38 with this armament and the same Merlin engines as the P51 :cool:

The wikipedia entry on the Hispano autocanon touches on the problem. The American showed interest in the British Hispano early on, but it appears the US manufacturers wanted to redesign the chamber somewhat. The result was that the weapon became prone to misfire. The USAF and particularly the USN had planned to phase out the .50 by mid war, but the American Hispano was delayed. Not until introduction of electrical firing post-war, did the US version become reliable enough for use in planes.

If the Americans had solved the design problems (or not redesigned the Hispano in the first place), Mustangs and Thunderbolts would have flown with 20mm Hispano canons rather than MGs. Luckily, the Americans could fall back on the .50, which gave adequate, but not great, firepower.

I wonder what drove them to 'improve' an already working design resulting US not having a cannon until 50's. But well, it worked out of ok concerning the outcome but would have been great to see / fly cannon packed late war fighters for US.

Anyone has any idea on the rate of failure the american models of Hispano's had?

I suggest everyone to read this excellent article:

http://www.quarry.nildram.co.uk/CannonMGs.htm

Excellent read and a comprehensive answer to my question. Thanks Buren!

The troubled history of the American Hispano (from the same author):

http://www.quarry.nildram.co.uk/US404.htm