Re: [Phys-l] Ballistics divertissement

[Roger Haar <haar@physics.arizona.edu>]

Hi,

	I believe my friends who are into guns have said things to imply that a 
blank would feel different then a bullet.  The problem is complicated by 
things like the burn rate of the powder . . .  But I think the simplest 
model is the that if the shells are loaded with the same amount of 
powder, there would be equal amounts of energy.

1.  If the blank wad massed m and exited with velocity v and the bullet 
massed M with velocity V, one would have 1/2 M V^2 = 1/2 m v^2.
2.  Recoil is related to impulse which is the change of momentum per 
unit time.
3.   The change in momentum is greater for the more massive bullet.
      ( For example, if M = 4 m, then v = 2V, and MV = 2 mv)
4.   The time for the change in momentum is shorter for the blank.  The 
burn rate is important here.

But some of the energy goes into K.E. of the "smoke" probably a greater 
fraction for the blank.  Also blanks usually are loaded with much less 
powder.

NO clear conclusions

Thanks
 Roger Haar

*******************************************************
Bernard Cleyet wrote:
> I must be very ignorant -- I thought the recoil was independent of the 
> bullet, i.e. only depended on the charge.  What one feels will depend on 
> the mass of the weapon.  On my way to Star Market I'll stop at Trigger 
> Hill and ask.
>
> bc, who thought rockets worked in a vacuum.
>
> p.s. reminds me of the M. Douglas film "The Star Chamber".
>
> John Clement wrote:
>
> > There might also be a noticeable difference in the smoke.  The blank may
> > produce more smoke coming out of the muzzle, while the live round might have
> > more smoke coming out of the chamber.  There might also be a difference in
> > the sound, but that would be very subtle and would not be noticed unless
> > they fire sequentially.  I suspect that the recoil question might be better
> > answered experimentally by someone who has experienced the difference
> > between a blank and live ammunition.
> >
> > John M. Clement
> > Houston, TX
> >
> >  
> >
> > > I watched a TV movie last night of the CSI variety, which revolved
> > >  around twelve jurors, dismayed by a torturer/killer going
> > >  free,  who conspired to train themselves to execute (!) a firing squad.
> > > This  program emanated from a country which does not
> > > (publically)  endorse state-sponsored torture, so there
> > > was a dramatic element.
> > >
> > >  A policeman casually mentioned, the shooters would know which of
> > > the twelve had the live round in the rifle - the recoil of course.
> > >
> > > So here's the point that puzzled me: supposing that each round had
> > > the same propellant charge, what would be the magnitude of the
> > > recoil/difference?
> > >
> > > I expect that it would be reasonable to have some numbers,
> > >  so let me pull these out of the air:
> > > bullet: 0.030 kg
> > > muzzle velocity: 500 m/s
> > >
> > >
> > >
> > > Brian Whatcott    Altus OK    Eureka!
> > >
> > >
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