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

[The_Shadow]

Hello Redline, I think what Benchrst was saying was that the barrels need to be a certain diameter for the strain gauges to calibrate correctly when installed. 

From Jim at RSI

"The problem is that a 10mm barrel is so thin it exceeds the normal
design parameters of the system.  It is designed so with a normal
bolt action rifle and 1.25" O.D./.308 dia chamber, anything that
exceeds safe pressures will flat line.

The one he made is not large diameter enough and the strain gauge is flexed as wrapped around the smaller diameter.

Looking at the Kaw barrel it is likely the purpose for this project...

[sqlbullet]

And, from green mountain I bet he is just getting a blank.

http://www.gmriflebarrel.com/bx3840-25-round-barrel-blanks-40-caliber-winchester/

[Benchrst]

The Kaw is 4.5", the Green Mountain will likely end up a 6" and a 10", since it ships as a 22" blank.

These 3 barrels will all have a strain gage mounted and be used for pressure testing?  That's what I was thinking you were getting at when you mentioned them earlier but I am wondering if it is possible to mount a strain gage to the Kaw barrel if it is this one; https://www.kawvalleyprecision.com/Kaw-Valley-Precision-4-5-10MM-4150-QPQ-AR-15-Barr-p/kvp-10mm-bbl-4.htm

I couldn't find the Green Mountain barrel you mentioned.
I found their website, assuming this is it; http://www.gmriflebarrel.com/
Can you provide a link to the specific barrel blank they offer that you're interested in?

Redline

Yes, that's the Kaw Valley barrel I purchased. I should receive it today, and if I'm lucky get it on the lathe Wednesday

The Green Mountain .40 blank can be seen here: http://www.gmriflebarrel.com/40-blank-40-cal-10mm-raw-round-barrel-blank-1-x-20/ (Sql was close )

The issue with my current barrel is the thin chamber walls - it's rate of expansion when fired is exceeding the systems data capture design. A 'number fix' from RSI improved the results but still resulted in cropped traces at upper pressures. Jim @ RSI stated that I could incrementally increase the 'number fix' until the issued is resolved, which I intend to try.

If I can get my current barrel to trace w/o crops I'll keep it in the mix, comparing it's results to that of the Kaw Valley and Green Mountain with future testing.

While each barrel's chamber is unique, and will provide unique results, the idea is to get similar results with three unique barrels - a validation if you will.

So much time, so much $, so close

[Benchrst]

Hello Redline, I think what Benchrst was saying was that the barrels need to be a certain diameter for the strain gauges to calibrate correctly when installed. 

The one he made is not large diameter enough and the strain gauge is flexed as wrapped around the smaller diameter.

Looking at the Kaw barrel it is likely the purpose for this project...

RSI didn't suggest the issue was how 'tightly wrapped' the gauge was, though that certainly may be a contributing factor.

Exactly, I purchased the Kaw Valley barrel because of it's generous chamber walls (a least in comparison to the 'turned round' Lone Wolf).

Finding an off-the-shelf solution has been a challenge, as most .40 barrels are configured for autos. I initially contacted Lothar, they were less than helpful, and the cost...

Also considered was TNW's ASR pistol barrel, but their website states you'll need a tax stamp to purchase (due to it being a drop in for the ASR). Didn't really want to hassle my way through that on the phone.

Good thing I'm persistent, otherwise I'd have an expensive dust collector

[Benchrst]

[Ridgerunner665]

That looks much better for pressure testing!

That's a lot of steel around that chamber.

[Benchrst]

That looks much better for pressure testing!

That's a lot of steel around that chamber.

Yes, .997 OD vs .623 OD

I'll profile forward of the chamber Wednesday and glue up a strain gauge, hopefully I'm testing this weekend

[Ridgerunner665]

I'm watching this closely... Very interested in seeing some numbers.

[The_Shadow]

Benchrst, wishing you all the best in this endeavor!  Good luck!

[REDLINE]

If I can get my current barrel to trace w/o crops I'll keep it in the mix, comparing it's results to that of the Kaw Valley and Green Mountain with future testing.

While each barrel's chamber is unique, and will provide unique results, the idea is to get similar results with three unique barrels - a validation if you will.

Interesting, thanks for explaining!  Can't wait to see the results unfold.

Earlier when you referred to Green Mountain reaming the barrel blank(s), is that reaming for the purpose of cutting a 10mm Auto chamber(s)?

[sqlbullet]

Yes.  Chamber ream.

[Benchrst]

Earlier when you referred to Green Mountain reaming the barrel blank(s), is that reaming for the purpose of cutting a 10mm Auto chamber(s)?

Yes, as SQL said, cutting the chamber.

The GM barrel is a "blank", it's rifled .40 but isn't cartridge specific (has no chamber).

Since it's a bull profile I can cut it into whatever lengths I need and ream (chamber) each section. Likely a 4", 6", and 10".

[REDLINE]

Definitely adds up to a nice selection of barrels to compare with and against.  As your project unfolds and develops I find myself more and more intrigued in anticipation of the well rounded and extenuating results it will ultimately produce!

[Benchrst]

Thanks for the encouragement guys!

The goal is to have a consistent, repeatable test platform up and running by July, and there's light at the end of the tunnel

Today's progress:

[The_Shadow]

Looking great...