10mm pressure testing
benchrst builds a Pressure Trace platform PART 3
1: Any attempt to duplicate / simulate, actual or otherwise, is at own risk.
2: I firmly believe this device is in compliance with ATF "can own it, can build it" guidelines.
3: I have no illusion that results will be definitive.
This project now spans four pages.
Part 1: The initial build.
Part 2: Updates and modifications.
Part 3: This page, additional updates.
Part 4: Progress
Results are here.
Continuing the discussion about glue(s)...
Strain gauge installed on the Kaw Valley barrel with RSI supplied glue.
Strain gauge installed on the Kaw Valley barrel with Loctite 401. 'User error' may have caused the voids, which could be causing lower-than-reality psi readings.
Which leads to...
200 XTP / 7.8 800X in LW barrel
Near same load in the Kaw Valley barrel (this load used Rem 9.5, LW load used Rem 2.5).
Barrel parameters are entered correctly in the Pressure Trace software, so either the modulus of elasticity is off (for one, or both barrels), or strain gauge adhesion is less than perfect.
As shown on page 2, this should answer the adhesion question.
On to 'generic' traces...
I won't have the Green Mountain barrel chambered and ready to test for at least a month, and until I have two similar results I hesitate to post specifics.
At 2 or 3 traces each the results are hardly definitive, but the exercise was an attempt to create a result that matched RSI's suggestion regarding my inquiry into low pressure readings.
Loads use new brass from same order, CCI 300 primers from same tray (seated with hand primer), powder measured on a Gem Pro 250 to within 0.02gr of intended. Brass sized on Lee die, flared to minimum required on Lee universal, seated on lee within two thousandths of intended. Crimp as specified.
Generic load "1": New Jagemann brass, Redding taper (noise at end of trace: "The dip on the trace is a momentary disconnection under recoil AFTER the bullet exited. The dip is not unusual and is often caused by vibrations transmitted through the surface of the bench to the module gage cable jack." ).
Generic load "1": New Starline, Redding taper.
Generic load "1": New Starline, FCD taper.
Generic load "2": New Jagemann, Redding taper.
Generic load "2": New Starline, Redding taper.
Generic load "2": Used Starline (case may be 1X or 8X), Redding taper.
Too tired for extrapolation :)
05.28.17 Just realized I have Winchester brass, and Sig, and Norma, and...
05.31.17 Green Mountain .40 cal barrel blank arrived, should have it on the lathe in the next week or so :)
Did a bit of testing today:
Note: Some loads may be above book max, use at own risk!
155 MG 12.8gr #7 CCI 300 1X (once fired) Norma brass, Kaw Valley barrel, strain gauge (SG) #2
155 MG 12.8 #7 CCI 300 1X Winchester brass, Kaw, SG #2
200 XTP 7.8 800X CCI 300 new Starline, Kaw, SG #2
Buffalo Bore 21B Kaw SG #2
Underwood 200 JHP (item 247) Kaw SG #2
Underwood 200 JHP (item 247) Kaw SG #1
I'm working towards an intelligently arrived at corrective PSI.
I'll get at least two chambers out of the Green Mountain barrel, so additional data points, or potentially additional confusion :)
I have three more strain gauges en route, and I'm considering alternative installation points:
1: Exactly as the others, centered over the case as it sits in the chamber.
2: Back a bit, just ahead of the case web.
3: Just forward of the case mouth, entering a zero value for case thickness in the software.
To simplify this for myself, either the modulus is off for both my barrels, or my chamber pressures are as reported. The GM barrel may, or may not, offer clarification.
06.01.17 From the Pressure Trace manual:
It does somewhat fall in line with my pressures vs published data.
For the Green Mountain barrel I may cut one chamber to whatever is 'regular', and order a custom reamer from PGT that's SAAMI minimum.
05.27.17 © 10mmreloaded @ gmail.com
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