The 50 caliber Browning machine gun bullet has a muzzle
velocity of about 2700-3000 fps, about Mach 2.5 but it is
slow by jet standards and has been replaced for aircraft use
by the 20 mm with higher velocity. The 45 ACP pistol has a
velocity of about 800 fps and is sub-sonic, the .22 LR HV is
just above Mach 1 but slows to below Mach 1 by 25-50 yards.
The 30/06 and other modern rifles have velocities from
2700-4000 fps depending on caliber and bullet weight. The
drag coefficient of a bullet of the heavy bullets used in
the 50 BMG and the 20 mm is such that the bullet does not
slow below Mach 1 for about 1/2 to 1 mile.

The bullet at a hyper speed exiting the muzzle would slow
faster than the same bullet fired from a stationary platform
because the drag increases by the square of the airspeed.


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"Jose" wrote in message
. ..
| If concorde (or and other supersonic
| aircraft for that matter) was fitted with guns then the
bullets would
| not be able to leave the muzzle
|
| I don't think there's anything special about being
supersonic to the
| basic physics involved (though it will add some wrinkles).
Before
| firing, there will be ram air pressure in the (forward
facing) muzzle.
| When the bullet is fired, there will be explosive chemical
pressure
| behind the bullet which will exceed the ram air pressure
in the muzzle -
| this difference will cause the bullet to accelerate down
the muzzle. At
| some point the pressure behind the bullet will begin to
decrease (as the
| reaction ends and the volume continues to increase), while
the ram air
| pressure will increase further up the muzzle (due to the
bullet pushing
| the air away). Given a sufficient charge, the bullet will
exit the
| muzzle and become a projectile. The speed of exit depends
on the size
| of the charge - obviously a dud would not eject the bullet
(but this is
| true of anything).
|
| Once the bullet exits the muzzle, it will slow down and
descend at a
| rate typical of a bullet. The plane flying behind or next
to it is
| independent and largely irrelevant, though it will
maintain speed and
| altitude due to its engines.
|
| Bullets typically are supersonic to begin with, so there's
nothing
| special here. Coming out of the concorde it will have an
initially
| higher airspeed than a typical bullet shot from the
ground, so it will
| decelerate more quickly. My gut feeling (I have never
shot a gun
| however) is that the bullet will have enough excess
forward speed that
| by the time it slows down to the concorde's speed, it will
be way ahead
| of the plane.
|
| Do fighter planes have guns that fire at supersonic
speeds? I suspect so.
|
| Jose
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