Re: Chamber Pressure

One could bond with epoxy to the barrel, a CEA-O6-250UW-350 strain
gauge.
One could bias up a Wheatstone bridge and amplify with AD8554 op amps
in an instrumentation amplifier configuration.
That amplified output could go into a storage oscilloscope.
One could then do some math with Roark's book on stress vs stain on
open ended tubes and Young's modulus for steel.
http://www.amazon.com/Roarks-Formulas-Stress-Strain-Warren/dp/007072542X
But the miss fit between your tube shape and the formula and the
accuracy of the position of bonding, will render the measurements too
inaccurate for absolute measurements without calibration.
One could calibrate his system with calibration ammo or factory ammo.
A rec.guns poster has generously sent me a copy of Rifle Accuracy
Facts by Harold R. Vaughn.
Thanks, Ken.
In that book Harold pressurizes the chamber with hydraulic fluid and
measures a static pressure of 15,000 psi with a dial gauge.
#From there he could extrapolate higher pressure measurements.
I think Harold uses an LM101 op amp from the 1960s. I think that
Oehler used a 1NA128 amplifier from some time since. The AD8554 I
suggest is better, but will not overcome the formula misfit and gauge
location problems.

Then there is the problem of what the pressure means.
If you can know the chamber pressure, what are you going to do with
it?
Compare it to the SAAMI registered average peak pressure for that
cartridge while working up a load?
If you are smart enough to built this test fixture, you should be
smart enough not to care what is registered with SAAMI for you own
personal handloads.
Why is that?
What is of interest in a work up in a strong rifle is not the
pressure, the effect of pressure on the brass.
I work up a handload to the threshold of short brass life, and back
off a safety margin.
Vernon Speer suggested that safety margin be 6% powder charge in his
1956 statement that shows up in Ackley's book.


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