From: "E.J. Totty", [EMAIL PROTECTED]
>NO WAY WOULD I ANNEAL USED PRIMERS, YOUR APPLICATION & THE USE THEREOF
>IS OK, BUT REMEMBER PRIMERS ARE SUBJECT TO CONSIDERABLY MORE PRESSURE.
>IF YOU'VE EVER SEEN SOFT BRASS FLOW UNDER PRESSURE, YOU WON'T DO IT
>TWICE.
>
>PRIMER CUPS NEED TO HAVE A CERTAIN HARDNESS, JUST AS THE CASE HEAD DOES.
>DON'T EVEN THINK OF IT.
>
>Walter.
Steve, & Walter,
Walter, I appreciate your concern -- especially as it is
directed at the safety end of the matter. Allow me to assuage
some of your fears in the regard as you express them.
First the lead-in:
In most modern semiautomatic firearms (notice I didn't
say all), the firing pin indents the primer for just long enough to
set in motion the event, and retracts to a recessed position.
In all the bolt action rifles that I have, the pin stays put
in the fired position until the bolt is retracted.
That being the case, in most rimless cartridges, once the
primer has set-off the propellant, the casing actually reacts slightly
along with the primer, with the primer reacting first. The primer
will, in some cases slightly slip out of the well, but as the case presses
up against the bolt, the primer is pressed flush with the case.
This is normal, because of the mechanical interference fit
the primer is designed for.
Indenting the periphery of the case around the primer
well in some military ammunition is just a safeguard to prevent
the possible expulsion of a primer as the case is ejected.
In the more severe cases of a hot load, the primer will
exhibit a 'flattened' appearance, along with correspondent damage to
the case head, in bolt action rifles.
I have not witnessed a case overload in semiautomatic
rifle -- yet, and hope never to, since from what I've read tells me that
it is a much more 'interesting' event.
That said, it is important to understand that point pressure
of a firing pin has more pressure exerted <per unit area> than the
pressure of the propellant, because if the propellant did exert a
greater pressure, then the primer indent would be very much less
evident upon observation.
Even in cases where the primer perimeter was flattened
by over pressure, as well as with the head of the casing, the primers
that I have seen still had a significant indent -- even with a floating
firing pin.
I suppose it might be considered academic to discuss
what the energy levels might be to distort a metal structure in one
direction, and then what the necessary energy levels would be to
distort it back in the opposite direction. And there is that matter of
fatigue to contend with . . .
It would make for an interesting experiment to take a
fired primer -- still retained in the casing -- and install the case into
a modified camber made for this experiment, and then gradually
exert a hydraulic pressure to observe when the primer begins to
revert in the opposite direction in the area of the pin indent, and
continue until the indent was almost nil.
One could use drift pin flattened appropriately,
attached to a spring tester, as a cheap test, although it would not
have the same accuracy as the hydraulic test, it would get one a
ballpark figure as to what pressures are involved.
Now, I would not consider reusing primer cups on an
everyday basis since, as Steve was kind enough to note <previously>,
that their relative abundance at shooter's stores makes the proposition
of reusing them less than economic.
It is, however, of interest to know that it can be done
effectively -- and safely -- if it has to be.
Analog: We all know about rubbing two stick together to
make fire. But do we do it at all today?
If push comes to shove, it pays not to toss out all this
knowledge merely because it is deemed iffy at best. Certainly
don't tell that to the gun makers in Afghanistan.
--
=*= =*= =*= =*= =*= =*= =*= =*= =*=
=*= Liberty: Live it . . . or lose it. =*=
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ET
Cybershooters website: http://www.cybershooters.org
List admin: [EMAIL PROTECTED]
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