From: dnewcomb@whale.st.usm.edu (Donald R. Newcomb)
Newsgroups: rec.guns
Subject: Let's get some term straight (was Re: Black-powder, Pyrodex or ?)
Date: 10 Jan 93 17:09:40 GMT
Organization: University of Southern Mississippi

In article <4269@eastman.UUCP> (MJ) writes:
#In article <9301071310.aa08701@claudius.pica.army.mil>,
#mfolenta@pica.army.mil wrote:
#Mike Folenta writes: (with a lot of my editing)
##  Black
##  powder (and Pyrodex, a black powder substitute that behaves like black powder)
##  gives more of a -shove- to a projectile as opposed to smokeless powder's
## -slap-.
##      Now, smokeless powder _explodes_.  It can produce -much- higher chambeX
#        *********************************
## pressures (we nowadays routinely use pistol loads of 40,000 cup and rifle loads
##  of 50,000 cup!)  Black powder doesn't even come close to that.  And something
##  has to hold/contain/resist those chamber pressures - like the gun.
#Flame time.  Black Powder is the explosive.  Smokeless powders and Pyrodex
#aren't.  You work for the government Mike , check it out.  Smokeless
#powders burn "fast".  And the wive's tale that black powder is incapable of
#high pressures is wrong.  I've read that testing was done on overloading
#muzzleloading rifles with pressure measurement equipment and pressures of
#100,000 psi were reached.  Black powder is not very effecient.  

I think we need to agree on definitions. Hatcher uses the term "explode"
to describe any rapid autocatlytic decompostion. The following extract
from _The_Thermodynamics_of_Firearms_ tends to back this up. In this most
technical sense, both black powder and smokeless powder explode. Smokeless
powder is capable, however, of performing one trick that black powder never
learned: detonation. I will be musing more on Robinson's book later, 
particularly on the subject of ignition. 

_Thermodynamics_of_Firearms_,_The_; Robinson, Clark Shove;
McGraw-Hill; 1943.

p.69

"Propellent powders may decompose in three ways, vis., by
detonation, by explosion, or by combustion.

"Combustion occurs when the explosive is burned in the presence
of air or other external source of oxygen, just as any combustible
material burns in external oxygen. Most propellent powders
burn by combustion in a manner similar to celluloid or camera
film, quietly, with little flame and no smoke.

"Explosion takes place in the absence of additional oxygen and
may be a relatively slow process, the speed of which depends on
the degree of confinement, or loading density. Explosion is a
surface effect, taking place solely on the surface of the powder
grain, never beneath the surface. Each layer of the surface must
explode away before the next layer underneath can do so. This
phenomenon is called 'explosion' because it is usually so confined
that  the process is rapid as compared with combustion and gives
an explosive effect.

"Detonation is an extremely rapid phenomenon, as much faster
than explosion as explosion is faster than combustion. The
whole solid mass detonates almost simultaneously, the detonation
wave proceeding through the solid mass with a velocity of several
thousand meters per second. Detonation is therefore a violent
process. If propellent powders are allowed to detonate, which
happens at times, the result is always a burst gun and other
serious effects.

"The products of explosion and of detonation are the same,
while those of combustion are presumably solely CO2, H2O and N2.
There is no sharp line of demarcation between explosion and
detonation. There is a long list of explosives whose individual
decomposition rates range all the way from very rapid detonation
to very slow explosion. Certain high explosives detonate only;
at the other end of the list is black powder, which does not
detonate. Smokeless powder will either explode or detonate,
depending on circumstances; when it detonates, it is a true
high explosive. Nitroglycerin, which normally detonates, can
be made to explode by blending it with certain other explosives
as is done in certain types of smokeless powders like cordite.   

-- 

Donald R. Newcomb                * Life only admits two states: 
dnewcomb@whale.st.usm.edu        * growing and dying. So what,
newcomb@usmcp6.bitnet            * if I've put on a little weight?