Case fill and burn %

[Huntaddict]

I took a look at some testing that was done in recent areas of temp variations. I wanted to know

Many brands claim that their powders are not temp sensitive, across certain types. Not all but most of the newer powders do carry that marketing around them. I wanted to see what NATO testing found with modern powders.

Cliff notes - in the graph they did find variations on velocities depending on powder, in this case Varget and TAC were tested. Varget is famous for being very temp stable.

Testing was conducted from -65 degrees to 140 degrees. I would venture that <1% of hunters are hunting in those conditions in the same year. Note: In "normal" hunting temps with Varget, -10 and 90 degrees Fahrenheit, the found approx a 15fps variance in velocity. Tac saw a more

Does this mean you have to change powder in your rifle? I have never been on a hunt or shoot where temps have changed that much in a day or two. Up to you.

However to me, I am zeroing my rifle at every hunt so unless I am seeing pressure signs hunting in 90+ degree temps, I am going to rezero, validate and go without ever changing my powder. Why i try to stay in the 90-94% range, to ensure I have my most accurate node without issue...at any temp.

 

[huntsd123]

newb reloader here. How do you tell your %? is it just off a manual for max load?

 

[Buttermilk]

I like to be 90+ % on case fill. I couldn't care less about burn %.

I shoot a lot of short barrel guns and have for 40 plus years. I've never had an accuracy problem with slow burning powders, and short barrels.

 

[Justice1327]

I pay absolutely no attention to case fill percentage, because it's a meaningless measurement outside of compressed loads. Using Lee's 1-Graon calc factor, I've significantly downloaded almost everything in the 30-06 case family, and my 264 WM.
My 204 is the daily shooting warhorse against vermin arrive the ranch. It's most accurate load is a fair amount below the Hodgy starting load. But the burning curve is stable.

Case fill percentage is not meaningless. You get a flash over your powder and you will see what I mean.

 

[FEENIX]

newb reloader here. How do you tell your %? is it just off a manual for max load?

I provided an example in #10 (a QL product). If you use QL or GRT, the software can project that.

 

[RegionRat]

newb reloader here. How do you tell your %? is it just off a manual for max load?

The popular internal ballistics models like Gordon's and QuickLoad give them as part of the output.

The case volume is based on the standards or user input. The powder volume is based on the density. The bullet geometry is known and with the seating depth, we can calculate how much internal case volume is left over.

Some manuals also list it.

Here is a screenshot example from Gordon's where I'll point to the case fill which they call load ratio. Just below it, is the percent burned estimate.

 

[M1A1ABRAMS]

newb reloader here. How do you tell your %? is it just off a manual for max load?

I suggest get yourself a reloading manual (S). And read it carefully. Don't rely on the internet for everything.

 

[twocan]

I was always taught 90% case fill. I see my best results with 90% or more.

I agree, but my best loads are at 95% for .338 Lapua Mag and .30-06 Springfield.

 

[Darkker]

Are you suggesting that being into or off the lands does not affect start pressure (and affecting peak pressure)?

Not at all what I'm suggesting, nor what people do in QL. But if we went with your question, think about the consequences of that...
QL which is supposed to tell YOU what pressures are doing, needs you to guess a pressure, so it can guess a result from your guess....

A deeper dive:
To your question about JTL, and pressures, your question is obviously phrased as a blanket statement. That's an incorrect QL mentality.
When you begin actually recording pressure and burning curves, the answer absolutely is in many circumstances; YES I'm saying jammed doesn't affect peak pressure, and it never affects start pressure.

Again, start pressure is atmospheric pressure. Then primer pressure, which is not affected by jump, then main powder charge.
So how can jump not affect initial pressure and peak pressure?
Very simply, progressive powders. Spoiler alert, GRT & QL don't know anything about them.

If you studied the RL-17 traces that I shared, you would have noticed they are completely different powders in those two applications. But if you run the simulations in QL, they are the same.
Because QL is foundationally built upon fixed Volume bomb calorimeter testing(for most powders). So in that single condition a burning curve is recorded, or calculated. Yes, it might never have been recorded, welcomed to the uselessness of burning rate charts...
QL keeps that base burning curve, and guesses how it would act in any other application; often asking you to adjust variables because it doesn't know how powder actually behaves.

Any program that priorities being able to change start pressure, as a "fudge factor". Instead of being able to change engraving pressure, is a child's toy.

 

[Mikecr]

Any program that priorities being able to change start pressure, as a "fudge factor". Instead of being able to change engraving pressure, is a child's toy.

But we couldn't do better with a reloading manual.
At least w/QL we have adjustments. Plenty of adjustments.

 

[Darkker]

But we couldn't do better with a reloading manual.
At least w/QL we have adjustments. Plenty of adjustments.

I would dearly love to know what you think "better" means.

Having options you don't understand, to effect an outcome you also don't understand; that was never rooted in much evidence. Is only "better", if driving your car alone, wearing a mask, complaining about the smells outside...

If I pickup my Speer book, they tell me that the Deep Curl bullets need different load data because of construction differences causing drastically different pressures.
Now they provide that separate load data, and that manual was a complete re-shoot of every cartridge in the catalogue. So for my $50, I have current(at the time) pressure tested data, saying don't use deep curl bullets with regular bullet load data, or bad pressures result.

Does your $300 Ouija board also show that pressures get dangerous?
If no, then obviously the $300 game isn't "better" than the book.
If yes, then the book is easily a better value for the same information.

So let's stretch out the legs of that Ouija board, and go toe-to-toe with something else that costs $300; ACTUAL calibrated pressure testing equipment.

308win, 42gr Win 748, 165gr bullet. Run the simulation with a cup & core bullet, then substitute in a Deep Curl. Post the burning curves and velocities that my dead great uncle divined from the Great beyond, then I'll post the actual traces of what happens.... You'll quickly learn how foolish it is, and why so many people think "signs" justify the utter stupidity of QL.
For an unbiased third party, call anyone with an honest ballistics lab, and ask them a very simple question: Do pressure signs magically appear the moment you exceed a cartridge's SAAMI MAP?

Or, go back up to the traces I already shared, and run the simulations for RL-17 in the 308 & Creedmoor. Does the Ouija board actually show the changing burning curve in each application, or does it simply try and smooth to fit? The answer is smooth to fit, because based on the fixed Volume bomb testing, there is only ever one burning curve, with a time adjustment.

What a manual tells you, is that there is a range of pressures that any combination operates predictably in; min to max. It tells you that some combinations begin behaving unpredictably as pressure increases(or decreases), which is why some powders stop a few hundred fps below others. That's all standard deviation calculations, as is beautifully explained on the SAAMI website. Only about a dozen of us, have actually read enough of the manual, or the SAAMI website to know that. What the manual doesn't tell you, is the specific pressure ranges they hold a powder to.

With some very simple pressure measurement, you will very quickly see those patterns emerge; and will see the standard deviations begin to rear their ugly heads. Does the Ouija board show you those things?
No it does not. Again, assumptions of a fixed burning curve with time dilation; and almost meaningless "adjustments" made by a user that doesn't know what he's doing with them.

 

[Justice1327]

I would dearly love to know what you think "better" means.

Having options you don't understand, to effect an outcome you also don't understand; that was never rooted in much evidence. Is only "better", if driving your car alone, wearing a mask, complaining about the smells outside...

If I pickup my Speer book, they tell me that the Deep Curl bullets need different load data because of construction differences causing drastically different pressures.
Now they provide that separate load data, and that manual was a complete re-shoot of every cartridge in the catalogue. So for my $50, I have current(at the time) pressure tested data, saying don't use deep curl bullets with regular bullet load data, or bad pressures result.

Does your $300 Ouija board also show that pressures get dangerous?
If no, then obviously the $300 game isn't "better" than the book.
If yes, then the book is easily a better value for the same information.

So let's stretch out the legs of that Ouija board, and go toe-to-toe with something else that costs $300; ACTUAL calibrated pressure testing equipment.

308win, 42gr Win 748, 165gr bullet. Run the simulation with a cup & core bullet, then substitute in a Deep Curl. Post the burning curves and velocities that my dead great uncle divined from the Great beyond, then I'll post the actual traces of what happens.... You'll quickly learn how foolish it is, and why so many people think "signs" justify the utter stupidity of QL.
For an unbiased third party, call anyone with an honest ballistics lab, and ask them a very simple question: Do pressure signs magically appear the moment you exceed a cartridge's SAAMI MAP?

Or, go back up to the traces I already shared, and run the simulations for RL-17 in the 308 & Creedmoor. Does the Ouija board actually show the changing burning curve in each application, or does it simply try and smooth to fit? The answer is smooth to fit, because based on the fixed Volume bomb testing, there is only ever one burning curve, with a time adjustment.

What a manual tells you, is that there is a range of pressures that any combination operates predictably in; min to max. It tells you that some combinations begin behaving unpredictably as pressure increases(or decreases), which is why some powders stop a few hundred fps below others. That's all standard deviation calculations, as is beautifully explained on the SAAMI website. Only about a dozen of us, have actually read enough of the manual, or the SAAMI website to know that. What the manual doesn't tell you, is the specific pressure ranges they hold a powder to.

With some very simple pressure measurement, you will very quickly see those patterns emerge; and will see the standard deviations begin to rear their ugly heads. Does the Ouija board show you those things?
No it does not. Again, assumptions of a fixed burning curve with time dilation; and almost meaningless "adjustments" made by a user that doesn't know what he's doing with them.

You remind me of Greg from PR.

 

[RegionRat]

So let's stretch out the legs of that Ouija board, and go toe-to-toe with something else that costs $300; ACTUAL calibrated pressure testing equipment.

For example, where are you suggesting we find pressure equipment for $300 and what do you mean by calibrated?

 

[FEENIX]

You remind me of Greg from PR.

Dang you, I almost choked with my spit.