Re: Gun barrel

[roger haar <haar@soliton.physics.arizona.edu>]

Hi,
	I think direct application of the gas laws may be complicated 
because the burn of the gun powder is not instantaeous.  My impression is 
that the burn time is a fair fraction of the time the bullet is in the 
barrel.  Different gun powders have different burn rates and if one is 
using the maximum charge of powder, the speed of the burn can be important
in keeping the gun together.  Gun people, just like engine people do not
speak of explosions in the chamber or the cylinder of the engine, but a 
controlled burn.

	An interesting phenonema with rifles shooting with heavy powder charges
is when the bullet breaks up shortly after exiting the gun ( the blue 
mist shoot) or breaks up before exiting which scars the barrel if it
does not casue the barrel to burst!

Thanks
roger Haar   U of AZ


*******************************************************
On Thu, 28 Nov 1996 PWILLIAMS@ACDM.RDC.AB.CA wrote:

> 	What about the effect of the gas laws: Charles and Boyles?  It seems to 
> me that the force accelerating the projectile is caused by the pressure of the 
> gases produce during the explosive combustion of the powder and detonator.  As 
> the projectile (piston) moves down the barrel (cylinder), the volume of the 
> gases increases, thus pressure (and force) drops.  Simultaneously, as the hot 
> gas expands down the cooler barrel, the temperature drops, again lowering the 
> pressure.  It should not take long before the pressure reduces enough so that 
> there could be no more acceleration.
>
> 	Does anyone know some typical values or ranges of the amount gas 
> produced and the initial temperatures?
>
> 	Would a hot barrel keep the gas hotter thus increasing muzzle velocity? 
> ... or does the expansion of the barrel allow more gas to "leak" thus reducing 
> muzzle velocity?
>
>
> Paul