Reading Pressure

[Weaver93]

Amen to that, at least when it's available.

I get a giggle out of the words "I pushed it to" this or that speed, "no pressure signs" and of then there is the good old "I ran a pressure test" today....

This is the reason I found the video so interesting. I know the rifle used was a bunch of parts that probably exceed anything that is regular retail, but what I found fascinating was that the level of estimated pressure (be it right or wrong) went from max to crazy in about 400 FPS of velocity.

Number of times I see someone post velocities that are two or three hundred FPS over max. Some even showing what I consider significant signs of pressure talking about how they think they are topped out. Heck, a couple had blowby soot up the headstamp where it squeezed out of the primer pocket. I just think that with the premium components we tend to use and the capabilities of the smiths we call on, sometimes we have no idea where we are when it comes to chamber pressures. I am as guilty as the rest because I know that rounds I have loaded and fired in my custom builds without the slightest signs of pressure absolutely locked up a factory rifle chambered in the same caliber (not intended, but it happened none the less). I know every rifle is different, but if you take the same load .5 grain under max, I doubt that would happen.

 

[cajun]

Maybe the hammer guys should watch this.

 

[MagnumManiac]

One thing I would like to add regarding reading your brass, is this:
If you find no other signs on your brass, but then the primer starts to crater, the bolt lift is normal, you have exceeded max pressure by about 8,000psi according to my Pressure Trace testing. The next increase will most likely show ejector marks.
If your rifle ALWAYS shows cratering, like a lot of REM 700's, then this advice doesn't hold up for them, ejector marks will be your first indication…

Cheers.

 

[cape cove]

@MagnumManiac
What is involved in pressure trace testing . Is it expensive or hard to do.

 

[MagnumManiac]

@MagnumManiac
What is involved in pressure trace testing . Is it expensive or hard to do.

Initial cost is around $800 if you buy more than the 2 piezoelectric sensors provided. Last time I checked they were $50USD each to buy.
I have 20 sensors and do not take them off until all testing is exhausted. I have been able to reuse only 3 after removal. The laptop requires quite a lot of ROM and storage.
It is very easy to use, it all goes into your laptop via the program and then will graph the results.

Cheers.

 

[Weaver93]

Initial cost is around $800 if you buy more than the 2 piezoelectric sensors provided. Last time I checked they were $50USD each to buy.
I have 20 sensors and do not take them off until all testing is exhausted. I have been able to reuse only 3 after removal. The laptop requires quite a lot of ROM and storage.
It is very easy to use, it all goes into your laptop via the program and then will graph the results.

Cheers.

Have you, by chance, compared your pressure results against Quick Load? I am just wondering what you see with piezoelectric sensors in comparison to the QL results. Video would have been more meaningful with this type of information.

 

[Mike D Texas]

What was the point of this video? Is it marketing for Alpha Munitions brass? I just don't understand the need to demonstrate what their data provided? If it is something no one should try to duplicate, and I certainly would not, I just don't see the point of the whole endeavor. It has been stated previously, but if you want 300WM performance, shoot a 300WM. Looking at the barrel and action, that is not a carry rifle. Just because you can, does not mean you should, and I still circle back to what was the point. Am I missing something?

I for one like to see videos like this. Many times they will debunk long lived theories. With the improvements in metallurgy, machining, powder, brass and the use of small primer high quality brass, I'm glad to see someone pressing the limits so we don't have to.

They did use a micrometer to measure case head expansion along the way as well. They didn't get much expansion until way over 60k psi. I want to say they didn't see anything over the long held .0005" until around 80k.

 

[Mike D Texas]

This is the reason I found the video so interesting. I know the rifle used was a bunch of parts that probably exceed anything that is regular retail, but what I found fascinating was that the level of estimated pressure (be it right or wrong) went from max to crazy in about 400 FPS of velocity.

Number of times I see someone post velocities that are two or three hundred FPS over max. Some even showing what I consider significant signs of pressure talking about how they think they are topped out. Heck, a couple had blowby soot up the headstamp where it squeezed out of the primer pocket. I just think that with the premium components we tend to use and the capabilities of the smiths we call on, sometimes we have no idea where we are when it comes to chamber pressures. I am as guilty as the rest because I know that rounds I have loaded and fired in my custom builds without the slightest signs of pressure absolutely locked up a factory rifle chambered in the same caliber (not intended, but it happened none the less). I know every rifle is different, but if you take the same load .5 grain under max, I doubt that would happen.

They used a BAT action the you can buy over the counter and chambered in a 1.250" straight barrel that you can buy off the shelf and they used Alpha SRP brass that you can buy off the shelf. And they used a reamer from Alpha that you can buy off the shelf.

Unless they are straight up lying, they didn't do anything anyone else could do.

 

[Mike D Texas]

One thing I would like to add regarding reading your brass, is this:
If you find no other signs on your brass, but then the primer starts to crater, the bolt lift is normal, you have exceeded max pressure by about 8,000psi according to my Pressure Trace testing. The next increase will most likely show ejector marks.
If your rifle ALWAYS shows cratering, like a lot of REM 700's, then this advice doesn't hold up for them, ejector marks will be your first indication…

Cheers.

Have you found that bushing the firing pin hole helps with primer cratering?

 

[Weaver93]

They used a BAT action the you can buy over the counter and chambered in a 1.250" straight barrel that you can buy off the shelf and they used Alpha SRP brass that you can buy off the shelf. And they used a reamer from Alpha that you can buy off the shelf.

Unless they are straight up lying, they didn't do anything anyone else could do.

Meant OTC firearms wise, my bad. I just think the components we are accustom to reaching for can mask things better than your run of the mill factory rifle.

 

[Mike D Texas]

Meant OTC firearms wise, my bad. I just think the components we are accustom to reaching for can mask things better than your run of the mill factory rifle.

Oh no.. in that case someone would be a fool to try that on a factory built rifle.

 

[Phil Rizzo]

Have you found that bushing the firing pin hole helps with primer cratering?

It definitely did help with the 2 m700 bolts LRI upgraded for me.

 

[Mike D Texas]

It definitely did help with the 2 m700 bolts LRI upgraded for me.

I'm thinking of having my factor R700 260AI bolt pin bushed and set up for SRP brass.

 

[MagnumManiac]

Have you found that bushing the firing pin hole helps with primer cratering?

On REM 700's it will fix the original issue, but cratering occurring on some actions as max pressure is surpassed is a good thing to me.
It tells me there is enough pressure to push the firing pin back and the primer is flowing around the firing pin nose and into the hole.
Not all actions do this, but most will if pressure gets high enough.


Cheers.