Re: Odd-ball conversions and left field questions

["Gareth Livergood" <garethlivergood@xxxxxxxxx>]

 > Something that seems to be forgoten, any airtight
> > item; voids in the frame,
> > cased ammo, etc. would only be traping 14 psi of
> > positive pressure
> > (atmospheric pressure at sea level is 14
> > pound-per-sq. in.).
>
> That's exactly what I was referring to when I said:
> > >You'd probably also want to check to see that
nothing on the weapon or ammunition causes a pressure
chamber that would trap either air or vacuum, causing a
 pressure rupture on exposure to vacuum or
reintroduction to pressure.

> > >
My point was that concidering the construction of almost all firearms, built
to withstand the rigors of use and combat.  That any void in the frame would
be more than capable of containing 14psi, a shaken soda can is under more
pressure.  I would postulate that even the weakest frame would contain 5 atm
(~70 psi), normal military weapons would be much higher, 10+ ATM, maybe.  A
shaken soda can is under more pressure.

> > The argument
> > for bleeding the cases of air doesn't seem valid
> > when most cases can
> > withstand several thousand psi and only split
> > slightly at the neck, if at
> > all (this is considering ignition outside a
> > chamber).  And a well seated
> > bullet requires conciderably more pressure to move
> > that 14psi.
>
>   I wasn't sure on how much ...
>Dive tanks are usually rated to 3000psi and
> are about 8mm-ish thick whereas cartridge cases are
> rather thinner. Igintion outside a weapon chamber
> doesn't normally rupture the whole round because it
> has a 'safety valve' in that the weakest way of
> rupturing the round is by propelling the bullet out of
> the case.

Exactly, the weakest point in a cartridge is the seal between the bullet and
the case and the bullet is usually seated with 20-40 pounds of pressure on
the loading press.  Normal handgun ammo has in-chamber pressures of 10k-18k
psi, (rife rounds can be much higher) the case is supported by the chamber
so it doesn't rupture, however with hot rounds loaded beyond normal
pressures you can get a split case and extraction problems.  With the
pressures that a cartridge case is designed for, 14 psi is insignificant
~0.01% chamber pressure.


> > With the pressure problems moot.  There is no reason
> > that a caseless weapon
> > would not work in a vacume.
>
> That's what I thought too. Hmmm...unless the pressure
> differential of the action of the bolt and the closed
> chamber would cause problems in some way? Erm, hmmm.
> My hangover is too great to allow me to comment
> logically.
>
>
The differance of 1 ATM would be to small for the mechanism to notice.  The
bolt might take a little more abuse on a gas operated weapon, but nothing to
cause an imediate malfunction, just shorten it's life a little, rattle
something loose sooner, nothing general maintenance wouldn't fix.

Anyone with more reloading experiance chime in so we can have the correct
numbers.

Gareth
>
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