Need clarification regarding Z1 P1 in Quickload

[Sheldon N]

And circling back to the original topic of PMax and Z1 intersecting as the basis for selecting a good load, I took the liberty of running a Quickload modeling of a known world record holding Dasher load done with H4895. It's interesting to see that the Z1 and Pmax lines don't align that well.

This leads me to think that Z1 and Pmax is probably best used to help pick what powder to use to optimize burn rate with desired Pmax. I'm sure that helps contribute to accuracy, but I wouldn't go so far as to say it's the best way to choose what load to shoot.

 

[savagedasher]

Powder burn is a chemical reaction. It starts with the primer, then it accelerates and burns more rapidly, then it reaches a "peak" then it starts to fizzle out and wind down. Easy to visualize, just imagine the last time you played with fireworks.

The Z1 line is the "peak" of the burn. Everything past that is the "fizzle", so to speak.

Pressure happens based on two things. One is the burn of the powder making pressure/gas, the other is the when (or time component) of that pressure and gas. The reason the when matters is that as soon as the pressure starts building the bullet starts moving. When the bullet moves the available space for the expanding gas is enlarged. Since the burn is accelerating and the bullet is also moving enlarging the space, you've got a moving target for where/when Pmax is going to occur. The longer it takes to hit Pmax the bigger the space available to do so, and as a result the more powder you can use and the more energy involved. This is precisely the reason why for a given max pressure, slower burning powders make higher velocities.

Once you are past Pmax the bullet is accelerating ever faster, the volume rapidly expands, and pressure drops as a result of the expanded volume. Simultaneously the powder, once past the Z1 line is in the "fizzle" stage and is mostly burned up already.

While Quickload doesn't draw you a line showing the percentage of powder burn, you can back into that figure by just changing the barrel length and seeing what the percentage of powder burn is. What you'll find is that 65-75% of the powder is burned in the first 4 inches, by 10 inches it's 90-95% burned, and all this burn is taking place a "digressive" manner meaning it's less energetic than the initial portion of the burn.

So essentially between 10 inches and 17 inches in the barrel, you have about 5% of the powder finishing up its "fizzle" in the lowest pressure part of the firing cycle when the pressure is falling rapidly.

All this is a bit long winded, but hopefully it helps you understand that what you've been saying isn't technically correct. Note that I don't disagree with you that H4350 is probably easier on the throat than Varget... I think that makes sense. Just not the way you've been saying it.

And circling back to the original topic of PMax and Z1 intersecting as the basis for selecting a good load, I took the liberty of running a Quickload modeling of a known world record holding Dasher load done with H4895. It's interesting to see that the Z1 and Pmax lines don't align that well.

This leads me to think that Z1 and Pmax is probably best used to help pick what powder to use to optimize burn rate with desired Pmax. I'm sure that helps contribute to accuracy, but I wouldn't go so far as to say it's the best way to choose what load to shoot.

After working with QL for over 14 years l know it works . Pull almost any load that other recomended and You will see . Same with the 95% .
If you change the internal volume or the burn rate They could align . It's not a powder I would use When I tested it had a big spike with temeture . N 550 was great till it got hot . 15 was the same . 16 looks good and from what others ar saying temperatures are stable
When I shoot the 32 lb of h4350 I have then I will look for others . Merry Christmas Larry

 

[dmoran]

Using QuickLoad and actually knowing it being two different things obviusly.
Besides errors in usage, repeatedly see the error in theories from it that don't live up to actual results.

Myself I used QL for about 3 years then stopped after getting a pressure trace system in 2006, because I found it did a poor job of lining up my actual pressures and velocities, and lost faith in it.

Much like a reloading manual, feel its a respectable product to base starting points, as long as the inputs are accurate and correct, and the output data is understood and assessed correctly.

Just my 2-cents
Donovan

 

[fredo]

And circling back to the original topic of PMax and Z1 intersecting as the basis for selecting a good load, I took the liberty of running a Quickload modeling of a known world record holding Dasher load done with H4895. It's interesting to see that the Z1 and Pmax lines don't align that well.

This leads me to think that Z1 and Pmax is probably best used to help pick what powder to use to optimize burn rate with desired Pmax. I'm sure that helps contribute to accuracy, but I wouldn't go so far as to say it's the best way to choose what load to shoot.

I agree with your premise, but that example is flawed...unless you have the actual data points of that world record load? IE, exact h2o capacity, powder burn rate tuned for temp, etc. etc... I'm sure both know that there is likely ALOT of painstaking effort gone into developing a WR load, beyond what that graph shows, or doesn't show. Nonetheless, I do agree with your point. z1/Pmax interaction is surely not the end all, be all with regard to surpeme accuracy development...

That said, would like to clarify:
By sharing some data points, I most assuredly wasn't implying that 'world record' accuracy could be achieved by simply tuning z1 & Pmax into alignment via QL. And, I'd hope no one here would be ignorant enough to assume, otherwise?

My point was, that by paying attention to the z1 / Pmax relationship, a reloader can streamline the process of finding a happy place with regard to bullet & powder combination(s). It does not, however, alleviate the need to test loads for real world safety & accuracy. Its simply another tool to use as a guideline. And one I've been paying attention to, with more than a few positive experiences to show for it...

Good shooting!

 

[JasonT]

Using QuickLoad and actually knowing it being two different things obviusly.
Besides errors in usage, repeatedly see the error in theories from it that don't live up to actual results.

Myself I used QL for about 3 years then stopped after getting a pressure trace system in 2006, because I found it did a poor job of lining up my actual pressures and velocities, and lost faith in it.

Much like a reloading manual, feel its a respectable product to base starting points, as long as the inputs are accurate and correct, and the output data is understood and assessed correctly.

Just my 2-cents
Donovan

This Z1/P1 may well be a thing...I've seen it work. But just like OBT nodes, I think Donovan is right about them being good starting points. We all know that even the most robust scientific theories don't always translate to the real world perfectly.

 

[dmoran]

I agree with your premise, but that example is flawed...unless you have the actual data points of that world record load?...

Good reply... and 100% correct that all relevant data points are needed and need to be accurate !.!.!

In Sheldon's WR reference, he was given full particulars from the WR holder (Tom Mousel) in-depth detail that included: - LabRadar velocity sessions w/ambient's, bullet measurements, case measurements & capacity, loaded round measurements, all from the bullets and cases being used. And of course, Sheldon's Ba adjustments to muck the labradar. I myself recorded all the data from Tom as he took measurements and read from his notes. Then passed all that on to Sheldon, to run the QL much up to it.

With that said, Sheldon's QL reference should be as accurate as QL is capable of mucking the load that Tom has been using so successfully to set those records and win those championships.

Very informative thread.... my own Thanks to all for replying !.!.!
Donovan

 

[Nvreloader]

Guys,

Did anyone notice that 2 different screens are being shown and compared to each other??

The first screen shown by Davey Boy is for Projectile Travel in inches,

The second screen shown by Fredo is for Bullet Travel time in micro seconds.

Kinda hard to compare any results??

Tia,
Don

 

[fredo]

Yes, enjoyable to bounce this stuff around! Re-confirms that there is no one cut & dried way to achieving exceptional results. Reckon that's what keeps things interesting for everyone?

One last thing, regarding the WR graph shot...
Although those lines may not be as closely 'stacked' as my examples, if I were looking for a Dasher load "cold turkey" (IE, with no other data to draw from) , the lines shown in that graph ARE close enough to infer that the powder/bullet combo is likely going compliment each other. The rest, is up to US to figure out, via systematic testing. And that's the fun part, ain't it?!?

 

[Davey Boy]

Much like a reloading manual, feel its a respectable product to base starting points, as long as the inputs are accurate and correct, and the output data is understood and assessed correctly.

Just my 2-cents
Donovan

x100 This is what I will use QL for, a tool for a possible better starting point only. It is interesting to note now that I know where to look, that my more accurate loads align P1 and Z1 a lot closer than some of the starting or even max loads were. It is a great tool ....but to be treated only as a tool. IMHO

Like Donovan said it was an interesting and enlightening thread. Thanks for all replies.

Dave

 

[Davey Boy]

Guys,

Did anyone notice that 2 different screens are being shown and compared to each other??

The first screen shown by Davey Boy is for Projectile Travel in inches,

The second screen shown by Fredo is for Bullet Travel time in micro seconds.

Kinda hard to compare any results??

Tia,
Don

Yes but the Z1 and P1 lines stay the same in all graphs I so do believe.

Dave

 

[fredo]

Guys,

Did anyone notice that 2 different screens are being shown and compared to each other??

The first screen shown by Davey Boy is for Projectile Travel in inches,

The second screen shown by Fredo is for Bullet Travel time in micro seconds.

Kinda hard to compare any results??

Tia,
Don

Don, that is just a graph diagram difference in QL.
The spacial relationship between z1 & Pmax lines are unchanged, regardless of which diagram is selected..

 

[Sheldon N]

This Z1/P1 may well be a thing...I've seen it work. But just like OBT nodes, I think Donovan is right about them being good starting points. We all know that even the most robust scientific theories don't always translate to the real world perfectly.

Very true, the target doesn't lie!

One thing I found interesting when modeling up Tom's WR load, it doesn't seem to fall anywhere near an OBT node either.

 

[savagedasher]

Very true, the target doesn't lie!

One thing I found interesting when modeling up Tom's WR load, it doesn't seem to fall anywhere near an OBT node either.

I think I said it hasn't worked for me .
Tom could of told you wrong But think not .
lol Larry

 

[savagedasher]

I was spot on on the data. I am going to give him some from another lot of powder and barrel I had that was phenomenal later tonight. I still have the fired brass from that one, and remember all the numbers like it was yesterday. It will be interesting because that lot of powder was different (slower).

It amazes me just how much of a caveman I am. Good information guys, even if it's mostly over my head lol.

Tom

Tom
We wouldn't expect anything less . Larry

 

[fredo]

Very true, the target doesn't lie!

One thing I found interesting when modeling up Tom's WR load, it doesn't seem to fall anywhere near an OBT node either.

One thing I'd find interesting is if that "WR" load would perform to "WR" standards in other rifles?
I'd sooner believe that load has been lovingly 'tuned' to one man's rifle, with that particular barrel & chamber spec, and his specific loading procedure & shooting skill to realize its potential...

IMPRESSIVE, no doubt!

But, to wrap back into the discussion, there's obviously more to a "WR load", than just the "load". In that regard, it doesn't surprise me one bit that trying to correlate its success back to something 'scientific' (like OBT, or QL musings), might not always 'fit' them, ideally...

I'm cool wit dat.

For conversation...

 

[dmoran]

@fredo -
Can't help but think that possibly the "Z1-Pmax line up theory" may hold up better with slow burning powders. Also am of the opinion that QL is inadequate to make consistent spot on predictions, but does have the ability to make referable approximations (as long as its feed and adjusted by accurate and complete inputs).
Donovan

 

[Sheldon N]

However, if you knew how many top notch dashers I've witnessed basically on the same load you would be amazed. We are talking 25 plus world records, over multiple barrels.

What would you say the balance between H4895 and Varget is for the top level Dasher loads you've run across?

 

[fredo]

What I'm looking for is a correlation between all the great dashers that I have either owned or had a front row seat to. Since I don't have quick load, nor am I smart enough to use it, I had Sheldon run the one example. However, if you knew how many top notch dashers I've witnessed basically on the same load you would be amazed. We are talking 25 plus world records, over multiple barrels. It may not be the pmax/z1 link, but maybe some other. It's unknown to me, but I find it interesting. I won't hold my breath, but possibly we can find a link? Then of course use that knowledge to find the perfect load when switching to a different powder?

Tom

Very interesting, Sir.

Does "basically" mean, the same exact load?
Or, the same bullet, launched at the same speed?

Have all those 25+ world records been shot with the same lot of powder?
Shot under the exact same atmospheric conditions?
Did all loads use the same lot of primers?
Same lot of bullets?
Where they shot in chambers cut with the same exact reamer specs?
From barrels with the same rifling profile & length?

I'll go ahead and assume that they weren't. Which actually lends credence to the notion that this "WR load" is simply one that is very forgiving, regardless of the above variables. Truly something worthy of study!

Forgive me for being so critical with all the questions, just trying to prove a point. Since your quest seems to be to find a scientific correlation to the success of this one load, it only makes sense to isolate & determine controls & variables. Without doing so & accounting for all of them, any attempt to find a solid 'scientific' basis for success simply can't happen. Unless one is willing to address & account for every possible variable, its not possible to draw a scientific conclusion. Ergo, expecting a program like QL to interpret 'perfection' in a graph, is folly...

I believe that you've discovered a wonderful 'sweet spot' with your rifle and load. Obviously, all those WRs prove that! If that 'sweet spot' load translates over to other like chambered rifles (despite all those other variables), I'd sooner believe that success is a function of just how 'sweet' that spot (load) is, for that particular cartridge. Don't sweat what QL or OBT predicts, or doesn't predict, just shoot that load and keep winning!

Still, I can understand wanting to quantify/measure that success with currently available computer models, in hopes of being able to replicate the same success. Who wouldn't!!! Just sayin', you might just be trying to catch lightning in a bottle. And the fact that a program like QL doesn't 'compute' or somehow graphically confirm the near 'perfection' you've apparently found, does not make the program any less useful as a guideline for basic reloading fundamentals. For that, QL will remain a wonderful tool to utilize & interpret potential results from...

 

[fredo]

 

[dmoran]

The success of H4895 in 6Dasher's really knocks a hole in the "Z1-Pmax line up theory", simply because the powder is to fast to get the Z1 & Pmax lined up. There for, if someone is trying to select a powder by "Z1-Pmax line up" for a 6Dasher, H4895 (and others similar) should not even be considered by the theory. But in reality H4895 has repeatedly proven to be one of the most successful and accurate powders for the 6Dasher.
Or so is how I'm seeing it play out.....
Donovan