Thread: Pressure Trace
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Old February 11, 2018, 11:05 AM   #30
Reloadron
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Join Date: June 8, 2016
Location: Cleveland, Ohio Suburbs
Posts: 1,330
This is like being a kid and getting that brand new bike for Christmas when there is two feet of snow outside and ice covered roads.

I just dug out an AR 10 takeoff barrel and looking at the barrel, floated handguard and gas tube it would be just about impossible to mount a strain gauge perpendicular to the barrel axis at the mid cartridge point. On the bright side:
Quote:
For this application the ideal placement of a strain
gage is as close to the center of the largest part of the
cartridge body as possible. This is typically an area
without taper so the gage will glue perpendicular to
the bore line and is not affected by metal of different
thickness.
Quote:
Unfortunately, placement in this location is not always possible if the action is equipped with a barrel nut
(Savage or AR with tube) and/or the cartridge is so short it barely
protrudes from the receiver. Satisfactory results can be achieved even if
the gage is glued over the case mouth but it should be at least ΒΌ inch
(7mm) away from metal of different thickness.
As long as you can find a spot which is not in a transition I would expect reasonable results. I would also have thought you should have seen something with the flick test? While not a pretty pressure curve "flicking" the strain gauge as they suggest should have triggered and yielded some bumps on the trace. You may want to go over that again.

Ron
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