Re: buoyant cannon balls

[brian whatcott <inet@intellisys.net>]

At 20:37 11/2/97 +0000, T J Folkerts wrote:
> On Fri, 31 Oct 1997 20:18:55 -0600 brian whatcott <inet@intellisys.net> 
> wrote:
>
>
> >  You can doubtless recall the cannon story about the Royal range trials.
> > By degrees more powder was added to a cannon charge to increase its range -
> > until a limiting charge, beyond which no more powder could induce an 
> > increase in range. And that of course was an early brush with the speed of
> > sound... 
> I don't follow.  Bullets and cannon balls can travel faster than the 
> speed of sound.  Why should the speed of sound be a limiting factor?
That's interesting. You have a reference for supersonic cannon-balls
I expect?   The drag properties of round ball grow specially
unfavorable near sonic speeds, I believe.

> Not that I am any expert, but couldn't this be related to the 
> combustion of the powder.  With a spark at one end, the powder can only 
> burn so fast.  At some point, the powder won't all have burned by the 
> time the cannon ball leaves.  Any more powder would just make a bigger 
> bang after the cannon ball had left.
>
> Timothy J. Folkerts 

I think this is a valid objection.
This has certainly been demonstrated with black powder rifles.
(filling the barrel fruitlessly with black powder, that is.)

I understand black powder is sensitive to packing density,
which can apparently vary the burn rate.
But evidence of the greater volume needed by black powder 
propellant is still available. Several extant calibers were
holdovers from black powder loads.
 For example, the popular and reliable handgun carried by
so many US police forces is still the 38 special revolver.

 This brass is currently loaded more than half empty with
smokeless powder, whereas it was formerly filled with black 
powder. The 357 brass which shares the same caliber has an even
longer case.

 I understand that this provides a convenient safety feature, 
in that 38 special shells can be fired from 357 weapons 
( and often are ) whereas 357 rounds will not fit older
weaker 38 special guns - the case is just too long.

Many beautiful Damascus barrels were burst when smokeless nitro
powder came along. One reasonably concludes that nitro can 
provide faster burning, higher pressure granules.

The question which arises from your argument is this:
"In the days of black powder long guns, was it possible
to provide bullets with supersonic speed?"

 Without offering supporting references I can suggest
the answer was 'yes'. One early design feature which encouraged
higher muzzle velocities was the waisted shell, with its
higher volume per cartridge length, and favorable venturi.

Sincerely,

brian whatcott <inet@intellisys.net>
Altus OK