LW's Gun choices?

[Pongo]

The hispano could never have fit in the engine mount of the 109..ever..
The germans(and the brits and the US for that matter) never percieved the Hispano as being superior to the 151. The Brits never manufactured the 151  because they doubted their industries capability to produce it. The US did produce the 151 in small lots but basically stayed away from 20mm till after the war.
Typhoon pilots never thought they had the 4 cannon 190 out gunned. The 190 pilots certianly never thought they were out gunned in the FW190.
For whatever combination of factors like enviromental issues and pilot training and many others. The hispano was not as good in ww2 as it is here. The 151/20 was all the gun that the LW thought they needed. The spanish figured out how to mount a hispano in the wings of a 109...I am sure that the Germans could have. If the germans were willing to have a gun as big and heavy as the hispano in their fighters they would have mounted a signifigantly more powerful weapon. A 30mm or something.
and
They did use the hispano. In one of their flying boats. So it was a LW service weapon..

But to answer Whels question. They used cannons cause that is what works to shoot down aircraft.  With the noted and unusual exception of the Americans. The mg was a secondary weapon carried on fighters in ww2 to back up unreliable or low magazine count cannons. When they had the kinks worked out of the cannons. the Mgs disappeared.

[Witless]

Hi

Regarding the reliability of Hispanos, in the book 'The Burning Blue' two veterans recall the events of The Battle of Britain, Wallace 'Cats Eyes' Cunningham and Hans-Ekkehard Bob. Cunningham includes squadron combat reports and also laments the reliability of Hispanos.

".....The bad news for 19F (the squadron based at Duxford) was that it was the first Spitfire squadron to be equipped with 2 x 20mm Hispano cannon. Their destructive capability was terrific, but they only held sixty rounds - six seconds firing - and stoppages were frequent, so few cannon were emptied."

He goes on to say that the CO and AOC decided to replace the cannon equipped planes with the 8 machine gun aircraft after a particularly bad mission.

[Karnak]

Witless,

That is only in regards to the initial attempt to install them in Spits, with Hispano Mk Is.  They changed the way they did the installation and moved to belt fed Hispano Mk IIs, and voila, stoppages pretty much went away.

I seem to recal the US Navy found that the M2 20mm cannon (a Hispano Mk II) suffered 1 stoppage for every 2,000 rounds fired on average.