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

[Benchrst]

Fred Meyer? I might have forgotten.  You live in the PNW?

I do, the ammo was included with a Parker purchase.

Reminds me, gunsmith still has that POS, it's been years (probably an ATF 'abandon').

Oh well

[Benchrst]

Was able to do a few tests today.


Note: Some loads may be above book max, use at own risk!


155 MG 12.8gr #7 CCI 300 1X Norma brass Kaw 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

[Pablo]

Wow. Really cool.

I may have missed it, but how do those traces stack against computer simulation load programs? (I can't think of the name of the popular one)

[The_Shadow]

Very interesting numbers...Just thinking ( I know that is very dangerous here ) and manipulating some numbers.

When you compare the numbers especially the IMR800X 200 XTP 7.8 800X CCI 300 new Starline Kaw SG #2
High 24541 psi,  Middle 22502 psi, Low 22323 psi
This load as listed by Hodgdon is shown as 1130 fps @ 32,500 psi

32500
-24500
8000 difference

BB 29,300 add 8000 = 37,300  (We both measured these as having 14.6 / 14.8 grains AA#9)
UW 28,600 add 8000 = 36,600
UW 31,200 add 8000 = 39,200

Taking in account the difference the BB and UW loads are inside the SAAMI MAP for the 10mm.

[Benchrst]

And that's what I'm (we're) 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 am 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 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.

[Benchrst]

Wow. Really cool.

I may have missed it, but how do those traces stack against computer simulation load programs? (I can't think of the name of the popular one)

Pablo

QuickLOAD predicts this:



Pressure Trace II is reporting this:



Both results, at this point, should be taken with a grain of salt

[sqlbullet]

Shadow did the same thing I immediately did...check pressures on the 800X load and derive a crude correction value to apply to the other loads.  Great minds?

benchrst, I agree they are to be taken with a grain of salt, but OTOH, your results have an appropriate curve and are consistent with each other.  This indicates your test rig is stable and repeatable.  Which means all that is needed is corrective values and you have a real winner there.

Additional chambers will be HUGE.  I expect the result to vary some, but will help us laymen see the differences the chamber cut can make. 

Once additional thought...The SAAMI pressure values are for a minimum chamber.  Such chambers are carefully cut to minimum dimensions and pressures in minimum chambers will be higher for the same load as a production chamber. 

These chambers are effectively production chambers.  While it is possible that this one happened to be cut to minimum, it is more likely that it is over minimum and will therefore report a bit low on pressure compared to a SAAMI test chamber.

[The_Shadow]

One of the most perfect Quick Loads screenshots that was given was for Power Pistol powder.
155 grain Gold Dot over 11.0 grains of Power Pistol making 1463 fps that shows 37,616 psi



Maybe Benchrst could do a comparison to get a benchmark testing this load with his pressure rig.

Then these two others were getting close to the magic 37,500 psi mark...
8.0 grains under a 200 XTP @ 1178 fps was shown at 36,881 psi
9.9 grains under a 180 Precision Delta FMJ @ 1289 fps at 36,236 psi

[Benchrst]

Included in the Pressure Trace manual:




I had read this before but forgotten about it. It does seem to support what's being reported in my chambers vs. published data.


The new GM barrel offers lots of possibilities (multiple chambers), and one thought is to cut a chamber with a standard reamer, and another with a custom PTG made to SAAMI min.

[The_Shadow]

It seems there is a fudge factor and finding that number will allow more precise info...
Article detailing some of the SAAMI testing;
http://archives.sensorsmag.com/articles/0599/0599_p93/main.shtml

Another publication with very detailed pressure testing equipment and setups for Ballistic Lab. (interesting reading)
http://www.pcb.com/Linked_Documents/Aerospace/AD-BallisticPressureGuide_LowRes.pdf?utm_source=Cal+Nation+%23106+%28August+2016%29+-+FINAL&utm_campaign=Cal+Nation+%23106+August+16&utm_medium=archive

I wish we could get our hands on the pressure test rig that Mike built and used for the SwampFox 10mm testing to add to the data.

[Benchrst]

Thanks for the links!

I had looked over PCB's site when I first got this hair brained idea, but decided selling my children to fund such a project probably wouldn't have worked out (average kids, don't think I would've got much for em').

A bit interesting (PCB pdf) is the statement that conformal sensors are located slightly behind the heel of the bullet.

My gauge placement puts it splitting the heel, at least with a 200gr XTP.



Curious if moving the gauge back would have any effect.

[REDLINE]

Very interesting numbers...Just thinking ( I know that is very dangerous here ) and manipulating some numbers.

When you compare the numbers especially the IMR800X 200 XTP 7.8 800X CCI 300 new Starline Kaw SG #2
High 24541 psi,  Middle 22502 psi, Low 22323 psi
This load as listed by Hodgdon is shown as 1130 fps @ 32,500 psi

32500
-24500
8000 difference

BB 29,300 add 8000 = 37,300  (We both measured these as having 14.6 / 14.8 grains AA#9)
UW 28,600 add 8000 = 36,600
UW 31,200 add 8000 = 39,200

Taking in account the difference the BB and UW loads are inside the SAAMI MAP for the 10mm.

My thoughts exactly.

[REDLINE]

Curious if moving the gauge back would have any effect.

Even if it would I don't see what would be gained.  Just my general thought and should be taken with a grain of salt!

[sqlbullet]

Taking in account the difference the BB and UW loads are inside the SAAMI MAP for the 10mm.

Maybe.  Possibly even probably.

My thinking:

These test are only of two-three rounds and are very preliminary.  A proper test would include a sample of 10 rounds, and would have no round exceed 40,500 psi corrected, or 32,500 based on the current correction factor.  And would have a MAP of 37,500.  The second Underwood 200 grain has only two data points, with a 3,486 PSI deviation.  If the low value is an outlier, and the average is closer to the high value, then the MAP (corrected) will be over 37.5K and chances are at least one round will exceed the 40.5K.

Of course, if the high value is the outlier, then this is just ammo loaded right to the max.

[Benchrst]

These test are only of two-three rounds and are very preliminary.

Exactly.

First challenge was to get functionality, that's been done. Second, show repeatability, getting there.

Still think this factors into what we're seeing.