Why do we want HE bullets? Are they really effective against well armored aircraft?
The idea, I think, is that HE bullets are also useful if they hit the wing. Currently, hitting the wings with ball bullets just means a hole circa fifteen millimetre wide. Using a high-explosive shell would mean a much wider one. [This uses that wings are too large to armour effectively]
Hitting the armoured body itself with a HE round will punch a bigger hole through it too, I believe, as planes are not as much armoured as tanks, for example.
This is one of the reasons I like the 15mm much more than the 10mm gun. The bullet is circa 3.375 times heavier (1.5^3), which means that it has 3.375 times the weight, 3.375 times the propellant resulting in the same muzzle velocity, but only 2.25 times the area when hitting, so much higher armour penetration.
@Bomber discussion:
The question is what we want to achieve, for all of this. We already have a CAS bomber (the Osprey), and actually no immediate need for one due to not fighting on the ground. We need it for its role as ship-attacking plane.
Now, if we want a heavy (that is, strategic) bomber to attack their production facilities and harbours, we at first need a high bomb load. This isn't achievable by close air support planes like the Osprey since this would make it too slow resulting in a very high vulnerability against both fighters and ground-level flak.
Using a high-flying design, we force the enemy to only use its fighters - hopefully after having to refit them - and make his flak inefficient or, in the case of low-calibre weapons, unusable.
I feel we should prioritize on a faster bomber rather than a High-flying, near-strategic Bomber. After all unless it is a carpet bombing mission, you cannot simply hope that you can drop bombs from 24000 feet and still hit the intended target.
I think that's pretty much impossible to do effectively while carrying a high bomb load. Taking the Osprey as example, we can probably get about a thousand kilo per engine at those performance levels. To actually be faster than the enemy lightning, let's say seven hundred and fifty. That seems pretty low considering that we also need defensive armament (since now reachable by enemy fighters) and are vulnerable to ground-based flak.