benchrst builds a Pressure Trace II 10mm platform (PIC heavy)

[REDLINE]

Very Nice

On the chamber end of the barrel, is the milled section basically the full length of the chamber?  And will the strain gage be mounted in the center (lengthwise down barrel) of that milled section?

[Benchrst]

Very Nice

On the chamber end of the barrel, is the milled section basically the full length of the chamber?  And will the strain gage be mounted in the center (lengthwise down barrel) of that milled section?

Yes, and no

The strain gauge needs to be mounted perpendicular to the bore axis.

Installed:



Case chambered, dummy round set for reference in relation to strain gauge placement (gauge needs to be about center of cartridge, and 1/4" from differing metal thickness).

[Benchrst]

The bits of black around the gauge connectors and substrate are what my rubber glove left behind after the glue setup, last time it was bits of skin 

[The_Shadow]

Looking great!  Hoping your endeavors will pay the dividends you are working so hard to achieve! 

[Benchrst]

Looking great!  Hoping your endeavors will pay the dividends you are working so hard to achieve! 

I should probably check in, see if I'm still married

[REDLINE]

Yes, and no

The strain gauge needs to be mounted perpendicular to the bore axis.

Case chambered, dummy round set for reference in relation to strain gauge placement (gauge needs to be about center of cartridge, and 1/4" from differing metal thickness).

The pictures are worth 1000 words!  BTW, nice job with the pics!

Is there a notion either way, if you change the parameters of the PTII to respond properly to the original thinner barrel, that it will throw things back off when setting up for the new thicker steel barrel(s)?

[REDLINE]

...last time it was bits of skin 

[Benchrst]

The pictures are worth 1000 words!  BTW, nice job with the pics!

Is there a notion either way, if you change the parameters of the PTII to respond properly to the original thinner barrel, that it will throw things back off when setting up for the new thicker steel barrel(s)?

Thanks!

No, each barrel has it's own profile that's loaded prior to testing.

[REDLINE]

Good to know.

[Benchrst]

Green Mountain .40 cal blank was in stock today so that's been ordered, should be about 3 weeks before it's chambered and ready to test.

Initial testing with the Kaw Valley barrel may happen this Friday, and would consist of matched published loads, factory loads, and misc loads.

The list can be seen here (link contains undocumented data, use at own risk!): http://10mm-reloaded.com/Pressure_Trace_II_platform/results/10mm_Pressure_Trace_II_pressure_test_results.html

If there's any specific interests I can try to work them in, the 'bullet library' of what I have available: http://10mm-reloaded.com/load_data/supplemental/40_cal_bullet_details.html

[REDLINE]

Can't Wait!

[Benchrst]

Did some limited testing on the 24th and ran into a few functionality issues: The striker spring was binding when compressed, slowing the striker on release. This caused the need for multiple restrikes; The barrel clamp profile isn't the same as the barrel, which allows a bit of left-or-right swing when it's cinched down - this created off-center primer strikes.

Solutions

Scribed line indicating the center of the striker allows for simple cartridge alignment.



Looking over the thrust block, centering the cartridge.



The striker release "keepers", kept in place by one bolt each, were rotating inward under the spring pressure, in turn binding release. Not having bolts short enough (impact the track on the underside) I drilled small holes in the base (where the "2nd" bolt would go) and filled with epoxy. Worked



Striker spring mod, epoxy and a washer.



Washer prevents the thin wire spring from bingding against the all-thread striker.



Fun part! He who sets his striker 'depth' too deep will blow primers!



Blew the striker completely out of the thrust block, bent one of the 'keepers', and trashed the striker keeper-pin link. Luckily I travel with really cheap pliers, back up and running in minutes



Results? I'm working on those

[Benchrst]

I won't have the Green Mountain barrel chambered and ready to test for almost a month, and until I have two similar results I hesitate to post specifics.

So...

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 0.02 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 will be explained later).



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.



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.

I've considered that including multiple chambers to the testing will only complicate results, even it they're similar, but it will be part of the process.

I'm beginning to think this is a multi-year process, and will involve independent labs.

Good thing I'm persistent, and don't care about retirement funds

[Benchrst]

And, apparently, I have nothing better to do on a Friday night at 7:55.

Pretty lame!

[The_Shadow]

Well, at least you are getting some data.  What was the powder and charge weight?