"Gord Beaman" ) wrote in message . ..
"Bob Martin" wrote:

For example... at 4000 feet, the bullets will only drop about 10
feet--random dispersion will be greater than that.


But that puts the centre of the dispersion pattern ~ten feet
below the aim point at that range doesn't it?

Yeah, but that's only about a sixth of a degree of arc...

also, a tank is what, 6-8 feet tall at least? Ten feet at that range is
very little to be concerned about... anyways, the point being that gravity
drop is less of a factor with the GAU-8 than with other guns.


I see...that's interesting...how do they do that? (your last
sentence I mean)

The GAU-8/A projectiles have a much better ballistic coefficient than
most aircraft gun shells because they are particularly heavy and
well-shaped, so they slow down less and arrive at the target more
quickly - so gravity has less time to act on them. They are not magic,
however, and will drop by the same amount as any other shell in the
same time.

By comparison with ground-based AA guns, the A-10's weapon also
benefits from the forward speed of the aircraft, and the fact that it
is firing 'downhill', which gives it a couple of built-in advantages.
However, if the AA gun is firing FAPDS that would restore the balance,
as an aircraft can't use this ammo.

BTW, the current Russian 30mm shells are almost as good as the
GAU-8/A's.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Discussion forum at: http://forums.delphiforums.com/autogun/messages/