I have this funny feeling that this one needs a bit of thought.

ok, so modern bullets already rotate very quickly, so i guess your idea is to make them rotate faster, in the hope that it will make them penetrate better. if rotating faster really makes them penetrate better, which i cannot see being a considerable amount if all, to have real influence the rotation would have to be so fast that most materials, especially denser materials, will have huge centrifugal forces, possibly so huge that they will just explode once they leave the containment of the barrel. but i am curious what principal founds the idea that high velocity rotation increases penetration, if you can answer that, maybe i would give this more thought.

Let me clarify more details, the usual canon has along tube from which the projectile is launched, the new weapon will also be like that but with a modification, there will be (I don't know the real word) a semi-shaft non-self-locking screw.

Concerning a proof, Do I need one?! Nothing stop the revolving thing, either penetrate or stop or vanish. about centrifugal force, No comment, Neither me nor you have tested that.

Not that I'm enthused about giving design advice to a person that discussing shooting down a model of fighter plane that my country deploys, I think you mean to make the projectile have two pieces: an outside piece turning and the inside piece that stays still? I don't see how this would be able to impart more energy on impact to the vehicle?

Yes, by spinning a projectile, you are able to impart additional energy to it--proportional to the angular velocity you spin, limited by aerodynamics. This could add a significant amount of additional energy. I don't know how much faster a bullet could spin as compared to it's current spin from the rifleing of the barrel. But you're still better off spinning the whole projectile rather than just an outside-hollow part because the equation to figure that energy also has 'm' for mass in it. More bullet, more mass.

Also, a spinning bullet won't necessarily impart it's energy to the target in a manner that will assist in penetrating it. Imagine if you hit a large rock with a spinning lawn mower blade. That energy will push the rock the direction the blade was spinning--it won't make a hole in the rock. I'm thinking the same thing for this.

But my knowledge of planes tells me that an F-16 probably only has thin armor and only in critical places. It's main defense it that you can't hit it. They also have systems to protect them offensively--if you shoot at him, he's alerted to see you and can shoot at you.

So are you a real terrorist or just a 15-year-old kid in Tennessee posing?

Maybe if I said MiG-29 Fighter, I would be no terrorist!!=)):))

I understand that only in recent times the word 'terrorist' has come to apply to a war-fighter without a big budget.

Using terror, that is, threats of violence to cause civilian people great fear (terror) is truely evil, but it isn't necessarily coincident with using a small-means to destroy an expensive plane.

But either way, F-16 or Mi-29, you're using small means to fight an entrenched government and you're going to be called a 'terrorist.'

But back to the weapon, I think if you combined a modern (powder explosion) gun with a rocket powered projectile, (like the gyrojet), you might be able to get the most energy to the bullet--more than by spinning. I wonder if someone has tried this?

http://en.wikipedia.org/wiki/Gyrojet

I'm not sure what a "semi-shaft non self-locking screw" is. You should try to describe it better. I'm guessing that you mean to make a projectile that drills or screws its way into the target. If so, then your idea won't work. The forward speed of a bullet is too fast for it to turn more than one revolution before it either penetrates or stops against a resistant material.

Also, increasing the spin rate of a bullet reduces its forward speed. The angular momentum(spin energy) is derived from the same energy source(gunpowder) as the forward motion. To increase the angular momentum, it will have to consume energy that would have otherwise gone into the forward motion. Lowering the forward velocity of a projectile will make it even less likely to hit the target.

Anyway, guns already have enough penetration power to penetrate most airplanes. As already mentioned by hrench, the real problem is that they're fast and thus difficult to hit.

One of the more obvious methods of hitting a difficult target is to use the shotgun method where a much larger cloud of projectiles attacks a fast moving object. A fast projectile can get a package of smaller explosive projectiles to the designated target area and then it explodes to create a large sphere of projectiles radiating from the secondary explosion. This is so obvious that it must already have been tried or is a standard weapon already or there is something wrong with the concept.