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I've owned the pre-Bluetooth pressure trace for a number of years. It is valuable. I think the wireless feature of the new version will simplify data gathering as mine has to go through an RS-232 to USB converter now, as well as having the wires run about.
The NATO EPVAT test method measures pressure just past the case mouth. The main drawback for using a strain gauge that far forward is the standard barrels have a shoulder contour there that is not cylindrical to glue to. You need the gage to lie flat on the steel with a thin glue line and with the long stripes of the gage foil paralles to a circumference line (perpendicular to the bore axis). The built-in gage equation solves for cylindrical steel. So if you want to use an AR rather than a bolt gun or an Encore, as I got for quick test barrel changing, a . You can get it in chrome-moly steel and do all your testing in it and avoid the whole steel modulus issue. I've measured .45 Auto rounds in a gaged Encore heavy barrel I had cut custom chambered for the purpose. It detects pressure through that thick thing, so it will be fine with the AR heavy barrels.
Incidentally, you can look up the modulus of elasticity for your type of steel on Matweb.com, and ratio it with that for 4130 and 4140 steel (they are the same 29,700 kpsi) commonly used in barrels. Divide your steel's modulus of elasticity by that number and use the result as a multiplier for the gage factor to create a correction.
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Great info--thanks for that--I know I can move the sensor further out from the case body--but as I do so the total mass of adjacent consistency declines--and the change in diameter from that of the chamber must be mathematically compensated for--or that's my rudimentary understanding from my initial conversation with Jim at RSI. He told me about matweb but said that stainless is so inconsistent in formulation it's hard to come up with a reliable baseline. Anyway I hope you won't mind dropping in and giving me pointers as I go down the path; )
My first blush survey of my barrels is that there seems to be no rhyme or reason to where the taper is, meaning it seems to be more a function of the particular manufacturer's barrel cutting scheme--so the chamber cut could be unpredictable in relation to it--I/m hoping the AR10 builds give me enough to work with in front of the barrel nut