Pressure signs vs velocity

denton said:

...For a given firearm, powder, and bullet, peak pressure is very highly correlated with muzzle velocity...

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"For a given firearm" is where the rub comes. Since no reloaders are using the "given firearm" that the test data was measured from, the correlation provided may not mean much. And since the data produced a non-straight line, I suspect there are variables at work in the "given firearm" that won't correlate well to other firearms.

BTW, what equipment/method was used to measure pressure in data you provided?

jmorris said:

This one is budgeted for the individual.

https://www.shootingsoftware.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=RSI&Category_Code=PT

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Strain gauges. Yea, if I was competing in 1,000 yard bench rest, maybe. I think I'll put that $700 toward a bottle of Pappy Van Winkle.

NMexJim said:

Do you have a method for determining pressure outside of basic ballistic calculation? I'd certainly be interested.

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No, I don't.

BBarn said:

"For a given firearm" is where the rub comes. Since no reloaders are using the "given firearm" that the test data was measured from, the correlation provided may not mean much. And since the data produced a non-straight line, I suspect there are variables at work in the "given firearm" that won't correlate well to other firearms.

BTW, what equipment/method was used to measure pressure in data you provided?

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What my statement says is: Pick a firearm, any firearm. Pick a powder, any powder. Pick a bullet, any bullet. Now instrument the firearm, vary the powder charge, and measure the peak pressure and the muzzle velocity. You will find that peak pressure is the main predictor/driver of muzzle velocity. (Or you can take a shortcut and do it in QuickLoad, which will give you the same result.)

There is no "rub".

The rule applies to any firearm you pick. The rule comes from physics and mathematics, and the field measurements are confirmation that it works.

Pressure was measured using the PressureTrace.

denton said:

What my statement says is: Pick a firearm, any firearm. Pick a powder, any powder. Pick a bullet, any bullet. Now instrument the firearm, vary the powder charge, and measure the peak pressure and the muzzle velocity. You will find that peak pressure is the main predictor/driver of muzzle velocity. (Or you can take a shortcut and do it in QuickLoad, which will give you the same result.)

There is no "rub"....

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The rub is, now you have inserted the need to instrument the specific firearm. 99+% of reloaders have no such instrument and aren't going to purchase one. Your earlier posts said nothing about instrumentation, but suggested that matching book velocity gave book pressure (with same barrel length).

Post 2 "If you reach book velocity with the same length barrel as the book, you are at book pressure."

Post 27 "If you have the same length barrel as the book, and are using the same components, and are getting book MV, you are also getting book pressure."

Data from a variety of firearms that show the same pressure trace pressures and the same muzzle velocities, would confirmed your earlier statements. In other words, I can go to a reloading manual, choose the exact components listed, and seat the bullet to the COL specified, and I will be at book pressure when I reach book velocity (accounting for barrel length), regardless of the firearm I've chosen. I'd be very pleased to see the data verifying the above.

BBarn said:

The rub is, now you have inserted the need to instrument the specific firearm. 99+% of reloaders have no such instrument and aren't going to purchase one. Your earlier posts said nothing about instrumentation, but suggested that matching book velocity gave book pressure (with same barrel length).

Post 2 "If you reach book velocity with the same length barrel as the book, you are at book pressure."

Post 27 "If you have the same length barrel as the book, and are using the same components, and are getting book MV, you are also getting book pressure."

Data from a variety of firearms that show the same pressure trace pressures and the same muzzle velocities, would confirmed your earlier statements. In other words, I can go to a reloading manual, choose the exact components listed, and seat the bullet to the COL specified, and I will be at book pressure when I reach book velocity (accounting for barrel length), regardless of the firearm I've chosen. I'd be very pleased to see the data verifying the above.

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Nonsense. You are grasping at straws and making silly arguments. The statement is a statement of what you would (again) discover if you performed that experiment, as many of us have.

I have already explained the underlying math and physics relating peak pressure and muzzle velocity. The experimental results are confirmation that the math and physics work as expected. Run the experiment as often as you like, on as many firearms as you like, and you will get the same result.

I have already explained the underlying physics and math behind the statement that if you duplicate book loading recipes, then if your muzzle velocity matches the books velocity, you are very close to book pressure as well.

jmorris said:

It’s also provable that many don’t, even if the bullet does have muzzle velocity over 0.

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This was also demonstrated in the article at the link.

denton said:

Nonsense. You are grasping at straws and making silly arguments. The statement is a statement of what you would (again) discover if you performed that experiment, as many of us have.

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My questions are sincere, and I think my "arguments" make sense. I don't have the equipment to run the experiment. You've run the experiment but are apparently unwilling to provide the data supporting your claim.

I will say that this discussion has led me to look at some reloading data where actual measured pressures (and MVs) are listed, and the correlation is what I would consider good to excellent. But its a bit hard to do since there is rarely a complete match of components. And it also appears that the data is from pressure test barrels which are probably high precision and may not be representative of what might be seen with factory production barrels.

Another issue for me is that I've never read of any suggestion in a reloading manual that the max powder charges listed can be exceeded as long as your MV doesn't exceed their data. If I understand your claim correctly, that is a reasonable approach to establishing the charge required for a particular firearm to match "book pressure".

You've run the experiment but are apparently unwilling to provide the data supporting your claim.

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I've posted the data in graphical form, and I have posted the corresponding ANOVA table. By what great stretch of reason do you say that I have not provided data? And, in any event, the rule comes from physics and math. The data are just a demonstration that the physics and math work.

I've never read of any suggestion in a reloading manual that the max powder charges listed can be exceeded as long as your MV doesn't exceed their data.

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And you won't, either. The liability is too great.

The head ballistician and Sierra did make exactly that claim. Federal jiggles the charge to get specified ballistics. John Barsness as been preaching that idea for years.

My position is actually a little more conservative than John's: The statement is true if you are working up your load and are seeing regular increases in MV as you increase charge. There are cases where MV plateaus with more charge, and you have to stay below that point. As long as you are below that point, the rule works. And you have to take into account engraving force. Partitions are harder to engrave than regular cup and core bullets. Hence the requirement to use the bullet specified in the book. Oh, and controlling temperature as SAAMI does. IOW, following the generally laid out reloading protocols.

Some barrels are "fast". They get higher than expected MV for a given charge. That means that they have some condition such as a tight chamber or short throat. The extra MV comes from high pressure. In those, you should not run "book" loads. Some barrels are "slow". If you have room for the powder, you can use more.

Also remember that if your barrel is not the same length as the one in the book, you have to adjust the permissible MV accordingly.

The data appears to show results for only one firearm/barrel. To support your claim, I'm suggesting a need for data showing essentially the same pressure@ same MV across multiple different barrels/firearms.

Mapping a particular barrel's pressure/velocity behavior is one thing. Saying that very firearm/barrel of the same length will produce the same MV at essentially the same pressure is a bigger claim, and needs to be supported.

You have apparently not read what I have posted. I am weary of repeating myself.

I think this is the fourth or fifth time: I have not generalized from a single firearm, as you claim. The claim comes from physics and math, which are general and apply to all firearms, and the data are a demonstration that the physics and math work. I have explained the physics and the math, and demonstrated that they work.

Not only that, but I have done the same test on multiple rifles, always with the same result.

You are free to believe or disbelieve, as you choose. Or to perform your own tests. Or to run QuickLoad and verify or disprove the results that way.

In any event, school is out.

I have looked multiple times at the graph and data you posted. I see no graph or data showing multiple test specimens (firearms/barrels).

As someone who spent 35 years designing products for trains, planes, and automobiles, I expect substantial claims to be supported with substantial data. Sorry I don't believe something just because you said it, and therefore flunked your class.