Thread: Pressure Signs in the 6.5x47

If no one ever mentioned pressure then it would be a lot safer. You are just comparing one made up number with another. Pressure is stress.

Brass strain is the result of stress. Too much stress and you get too much strain. If you are not getting brass strain, you are not getting a lot of stress. Pressure creates stress, stress creates strain. Pressure is homogeneous. Stress does not always come from pressure. If the case fails to grip the chamber wall you get massive stress on the bolt lugs without a lot of pressure.

A chronograph tells you more than anything else. You will see max pressure over the chronograph with 6.5x47L before you see any strain, at least with 2209 anyway.

Originally Posted by Tussock

You will see max pressure over the chronograph with 6.5x47L before you see any strain, at least with 2209 anyway.

If this was true then it would be commonly known and accepted that load development with the 6.5x47 should be approached differently rather than looking for pressure signs. I have not seen velocities increase with 2209 anything other than in a uniform monotonic way. Please tell us what you know from your experience as you appear to have operated up where things became... interesting?

Originally Posted by Puffin

If this was true then it would be commonly known and accepted that load development with the 6.5x47 should be approached differently rather than looking for pressure signs. I have not seen velocities increase with 2209 anything other than in a uniform monotonic way. Please tell us what you know from your experience as you appear to have operated up where things became... interesting?

Nope. Never seen anything interesting. Just saw the velocity gains start to taper off. Were you getting the same gain per increment of powder linearly?

Why do you have no "pressure signs" if you have pressure?

Originally Posted by Tussock

Nope. Never seen anything interesting. Just saw the velocity gains start to taper off. Were you getting the same gain per increment of powder linearly?

Why do you have no "pressure signs" if you have pressure?

Yes, no flattening-off of velocity increases with incremental increases in charge weight.

You know very well that in using the term "pressure signs" I am referring to dimensional changes in the case and primer that are commonly used by shooters as an indication that peak pressures on firing have reached levels widely accepted as a limit for safe operation. Rather than being a contrarian are you instead prepared to provide the data where you saw velocity start to taper off so it can be considered as alternative method for load development for this cartridge ?

Originally Posted by Puffin

Yes, no flattening-off of velocity increases with incremental increases in charge weight.

You know very well that in using the term "pressure signs" I am referring to dimensional changes in the case and primer that are commonly used by shooters as an indication that peak pressures on firing have reached levels widely accepted as a limit for safe operation. Rather than being a contrarian are you instead prepared to provide the data where you saw velocity start to taper off so it can be considered as alternative method for load development for this cartridge ?

No, I am simply pointing out shooters use "pressure signs" for relative pressure. You are mixing this with absolute pressure. Your "72,000 PSI" has a margin of error of about 10,000psi. When you see case deformation which shooters refer to as "pressure signs" these are not actually pressure signs.

Its just a lack of understanding which fortunately does not seem to matter that much as few people die handloading. It is a dangerous misconception of the relationship of pressure, stress and strain.

If you get case deformation the source may or may not be pressure. It could be you have lubed the inside of your chamber causing excess bolt thrust. It is much safer to be aware case deformation has more sources than pressure.

Its is also safer to be aware of what is happening to the action to create each different type of case deformation. Sticky bolt lift is a different thing to ejector marks. One is chamber expansion and the other is bolt thrust.

There is no reason to care about absolute chamber pressure because you have no way of knowing what it is. The number is completely irrelevant. You can produce dangerous case deformation at very low powder charges in a variety of action/brass combinations. Think of all the people loading random cheap once fired factory brass? What you said about the 6.5x47L is true for all of them. The brass is weaker, so you have no idea where its failure point will be.

If you have no case deformation, no sticky bolt lift or any other form of STRAIN then it is unlikely you need to worry about strain.

My point is you are confusing people in a way that is dangerous. If you want to get all high tech and roll out quickload, then why can't we switch to using the proper language for this?

I am not being contrarian, I am pointing out the conventional language of shooting, while completely functional in a practical sense, can't be used for the kind of theory you have.

Stick with convention. Even though "pressure" is nonsense, those "dimensional changes" used by shooters are all you care about. You start with small ones and you progress to case separation. If they are not there, then you don't have a problem, end of story.