Pressure or not?

[Shane Lindsey]

You have ejector print ( ) before the start of the swipe. Looks like over pressure to me.

 

[waveslayer]

Longer seated bullets don't mean more pressure like handgun calibers. It's the opposite @Darkker . It's higher pressure if the bullet is jammed into the lands. But your other info is good. Pressure testing can only be achieved with the proper equipment hooked up to the pressure testing barrel. I think he's, the OP is referring to over pressure. All cases experience pressure. It's what safe for that chamber, Ackley or not. The case will tell you, like the pictures he provided

 

[Darkker]

Longer seated bullets don't mean more pressure like handgun calibers.

Let me make sure I understand your claim here:
Your claim is that pistol and shotgun powder somehow magical operate completely backwards, compared to rifle powder... That's quite an amazing claim, you better post your pressure Traces justifying that claim...

For those capable of reading and are curious about this, lookup Dr. Lloyd Brownell's absolute chamber pressure in center-fire rifles, done at the U of M in 1965. Here's the basics, think of a standard chart. Vertical axis is pressure, horizontal is jump to lands. Draw yourself a "V" with a rounded bottom, and that's how pressure actually works. When you start jammed, pressure is high, as you increase the jump to lands, you allow more time for the gas to bleed off around the bullet before land engagement. At a certain amount of depth, which is cartridge dependant; you will eventually eat up enough case volume with the bullet. Which will begin to play with flow geometry and therefore burning rates. I E. The right side of the "V" where pressure begins to go back up. Again it isn't linear and simple line a perfect "V", but it gets the point across.

Pressure testing can only be achieved with the proper equipment hooked up to the pressure testing barrel.

I've been pressure testing for the better part of two decades, I'm quite familiar how it's done...
Which is why I also find it shamefully outrageous to say it hasn't been available to the general public.
Here's the difference between anyone of the fine people on this forum, and this mouth-breathing redneck: I can smell a carpetbagger from a mile away. I don't like being lied to, and I reject mindless faith claims of magic. So I buy tools that allow to me actually measure and learn.

The case will tell you, like the pictures he provided

The case will "tell you" that it reached plastic deformation, but not what pressure that occurred at. And what he has pictured isn't plastic deformation, it's friction.
Ask yourself this:
If the ejector is functioning properly, it's completely recessed within the bolt face when a case is against said bolt face. So normally when you rotate the bolt against the case in the chamber, it doesn't scrape the case. Are you suggesting that when the pressure is high, the rifle somehow magically knows that, and pushes the ejector out harder. Thereby letting you know that SAAMI MAP has been matched, by the scratching of the case head?

 

[waveslayer]

Let me make sure I understand your claim here:
Your claim is that pistol and shotgun powder somehow magical operate completely backwards, compared to rifle powder... That's quite an amazing claim, you better post your pressure Traces justifying that claim...

For those capable of reading and are curious about this, lookup Dr. Lloyd Brownell's absolute chamber pressure in center-fire rifles, done at the U of M in 1965. Here's the basics, think of a standard chart. Vertical axis is pressure, horizontal is jump to lands. Draw yourself a "V" with a rounded bottom, and that's how pressure actually works. When you start jammed, pressure is high, as you increase the jump to lands, you allow more time for the gas to bleed off around the bullet before land engagement. At a certain amount of depth, which is cartridge dependant; you will eventually eat up enough case volume with the bullet. Which will begin to play with flow geometry and therefore burning rates. I E. The right side of the "V" where pressure begins to go back up. Again it isn't linear and simple line a perfect "V", but it gets the point across.


I've been pressure testing for the better part of two decades, I'm quite familiar how it's done...
Which is why I also find it shamefully outrageous to say it hasn't been available to the general public.
Here's the difference between anyone of the fine people on this forum, and this mouth-breathing redneck: I can smell a carpetbagger from a mile away. I don't like being lied to, and I reject mindless faith claims of magic. So I buy tools that allow to me actually measure and learn.


The case will "tell you" that it reached plastic deformation, but not what pressure that occurred at. And what he has pictured isn't plastic deformation, it's friction.
Ask yourself this:
If the ejector is functioning properly, it's completely recessed within the bolt face when a case is against said bolt face. So normally when you rotate the bolt against the case in the chamber, it doesn't scrape the case. Are you suggesting that when the pressure is high, the rifle somehow magically knows that, and pushes the ejector out harder. Thereby letting you know that SAAMI MAP has been matched, by the scratching of the case head?

no you are correct on the pistol and shotgun powder, that was my error.
I wish we had a good way to measure actual pressure... Like when guys send barrels off to get the +P throats done.... there is only so much you can do.
Unfortunately there was a new rifle company coming out with some crazy stuff that was allowing insanely high pressures, they were doing work with RUAG to make some special brass for the pressures they were running. To make a long story short, the guy is in jail and it's a crazy ATF nightmare for some stupid things this guy did. I was lucky to get my money back/investment for a rifle.
I wish we could get a good way to measure pressure like MV.

 

[ka30270]

Let me make sure I understand your claim here:
Your claim is that pistol and shotgun powder somehow magical operate completely backwards, compared to rifle powder... That's quite an amazing claim, you better post your pressure Traces justifying that claim...

For those capable of reading and are curious about this, lookup Dr. Lloyd Brownell's absolute chamber pressure in center-fire rifles, done at the U of M in 1965. Here's the basics, think of a standard chart. Vertical axis is pressure, horizontal is jump to lands. Draw yourself a "V" with a rounded bottom, and that's how pressure actually works. When you start jammed, pressure is high, as you increase the jump to lands, you allow more time for the gas to bleed off around the bullet before land engagement. At a certain amount of depth, which is cartridge dependant; you will eventually eat up enough case volume with the bullet. Which will begin to play with flow geometry and therefore burning rates. I E. The right side of the "V" where pressure begins to go back up. Again it isn't linear and simple line a perfect "V", but it gets the point across.


I've been pressure testing for the better part of two decades, I'm quite familiar how it's done...
Which is why I also find it shamefully outrageous to say it hasn't been available to the general public.
Here's the difference between anyone of the fine people on this forum, and this mouth-breathing redneck: I can smell a carpetbagger from a mile away. I don't like being lied to, and I reject mindless faith claims of magic. So I buy tools that allow to me actually measure and learn.


The case will "tell you" that it reached plastic deformation, but not what pressure that occurred at. And what he has pictured isn't plastic deformation, it's friction.
Ask yourself this:
If the ejector is functioning properly, it's completely recessed within the bolt face when a case is against said bolt face. So normally when you rotate the bolt against the case in the chamber, it doesn't scrape the case. Are you suggesting that when the pressure is high, the rifle somehow magically knows that, and pushes the ejector out harder. Thereby letting you know that SAAMI MAP has been matched, by the scratching of the case head?

That makes more sense to me and is how I have understood the pressure curve. When you get closer to the lands pressure goes up but pressure also goes up again when you take up more space in the case as you seat deeper. I believe the SAMMI COAL is what the designer deems as the "correct coal for proper pressures" or the best average coal for a variety of "factory chambers".

 

[ka30270]

Okay I removed and examined the spent primers. Correct me if I'm wrong but I'm not seeing excessive pressure compared to the new unfired primer.

 

[Darkker]

I wish we had a good way to measure actual pressure... Like when guys send barrels off to get the +P throats done.... there is only so much you can do.

"We" do have a good way to actually measure pressure, as I've been saying for as long as I've been on this forum. I've literally begged people to but a Pressure Trace, and actually start measuring pressure. But stupidity is more communicable than the flu, so people spent the same amount of money on a magic eightball instead. The PT folks have retired, so now you'll have to find a used one, or go back to paying to Zeus.

 

[308win]

Okay I removed and examined the spent primers. Correct me if I'm wrong but I'm not seeing excessive pressure compared to the new unfired primer.

I may have missed it, but is this brass Virgin or 1st firing in your rifle?

 

[ka30270]

Brass was virgin before this firing

 

[308win]

Brass was virgin before this firing

In your rifle? If this is the 1st shot in your rifle, I wouldn't be too worried? Your primers look good to me. As others have said, possible mechanical issue?

 

[308win]

In your rifle? If this is the 1st shot in your rifle, I wouldn't be too worried? Your primers look good to me. As others have said, possible mechanical issue?

Sorry, was typing when you replied again. See if a fire formed piece is doing the same thing after sizing? May just be a little extra space in that chamber?

 

[Hard rock]

At this point unless you have access and knowledge on how to use pressure gage equipment , I would make sure I wasn't jammed into the lands ,as you stated you were over col.I would then back off powder charge 5 to 10 percent and work back up using a chronograph comparing vel to book vel . Before doing anything I would check primer pockets to see if they are still tight , loose primer pockets are a very good indicator of max pressure , as you probably already know . Good luck and keep us informed

 

[dogz]

I've been handloading for 30+ years but this I need some help with. This is near max powder but my coal is longer than book obviously. This is a Tikka 308 Win and I understand this is 7.62x51 brass and I have taken that into account. It's actually made by Naamo which is Lapua so this has been very consistent brass. OKAY on to my question….. Does this look like over pressure or a scrape? It appears to be from the cutout for the extractor and I don't see any ejector swipes. I haven't chronoed it yet I was trying to find my pressure limit. No sticky bolt lift.

Thanks

What was the load?

Been about a month, have you got back to the range to run it over a clock?

Keep in mind that "Pressure equals speed and speed equals pressure"