QuickLOAD way off from reality. Solutions?

[JKPhoto]

What do you mean change the slope of the velocities?

What I meant was that if I am doing a ladder test, and try to adjust to the actual velocities, that the Ba adjustment I make affects all the velocities similarly and then power charges that are 1-2 grains away from the point I chose to adjust to, do not adjust accordingly. I get that the burn rate changes with load density etc, but should that not be accounted for in QuickLoad?

So I have been looking for a way to adjust something(s) that would make "all" data points match up to tested velocities.

 

[TommyBreaux]

I have been running QL since 2010 with excellent results. Early on I was also having difficulty getting it tuned. Both the original developer and the ballistician at Western powders weighed in and helped me out. Each new combination of components needs to be tweaked. It's not a one and done process, nor do I think having "friends" model a load for you, is a good idea, unless you give them a reasonable amount of load/velocity data and all your cartridge and rifle specifics, AND they know what they are doing. I did my master's thesis on ballistics modeling, so I understand how to run a model. This is a model. I do not claim to be an expert either. So do what is right/safe for you - not what some "expert" said on the interwebs! Having said that. Here is what I do - for every unique combination of components/rifle AND every change in powder lot.

Start with actual COL, barrel length, bore cross sectional area (usually only necessary if you are having difficulty getting good results). Load 5 shells of your intended components in .5g powder increments, within the published max powder charge. Get velocities from a Labradar or magneto speed, preferred. Tweek the case capacity value down if your real velocity is faster than the model, up if the model is showing faster velocity than reality. I typically stop tweeking case capacity after I get ~5% from measured case capacity and move on to shot start/initiation pressure if I am still not matched up.

Next I tweek the shot start/initiation psi variable up if I still need to speed up the model, and vice versa.

At the time I was told that the shot start/initiation value in QL was not a measured value, but a starting point largely based on bullet design. Mono bullets were using an un-grooved assumption, so likely newer TSX, TTSX, LRX designs the shot start pressure can be lowered to get your model to be accurate.

That was the process provided by the ballistician at Western, who used QL extensively for load development then measured the results in a pressure barrel. I was told to be mindful of the pressure = velocity equation. You can't have one without the other. If QL says you are at 65,000 psi at 3100 fps - believe it!

Mr. Slamotrutta, I have to ask you, why to do you tweak the case capacity to calibrate the load? That is the one thing that is easily measured and verified? In Mr. Long's paper, one of his suggestions to calibrate the load is to modify the bullet weight slightly. I don't understand that either. If you know the bullet weight and the bore diameter and case capacity why would you fudge them? None of those variables change with temperature to any great extent that would be measurable. On the other hand, Ba (Powder Burn Rate), is temperature dependent and varies powder lot to powder lot. So what difference does it make if you vary it +/_5% to get the load and the measured velocity at temperature to match. Starting Pressure, can be jump dependent depending upon whether the bullet is jammed or has clearance but it should be constant for that bullet in that gun. I have seen one equation where the initial starting pressure is dropped by so many psi for every two or three thousandths off of the lands the bullets are seated. I don't think that equation was verified by actual pressure barrel measurements in a ballistic lab. Just like too many cooks spoil the broth, too many variables cloud the results!

Thank you for your insights.

 

[capona]

QL does provide a default value for each cartridge. I changed the value down until I got the real world velocity. That is the value in "QL H2O". I only posted it to show how outrageously far off the model was from my real conditions.

"Real H2O" is the actual capacity of my cases, which is what was used to get the "QL FPS" value (which was way below reality).

"QL Charge" is the charge QL required to get the "Real FPS" value, using "real H2O" values.

That is one of your issues if you are using the default cartridge value in the pulldown. You need to measure your actual fired/trimmed brass for that value. For example in win 308, there can be a 3 grain difference in H2o capacity between lake city and lapua or winchester brass. QL doesn't know what you are using for brass. You need to tell it by measuring the h20.

Use several values of H20 by a few grains and check the difference it makes in your QL output.

 

[Veteran]

What I meant was that if I am doing a ladder test, and try to adjust to the actual velocities, that the Ba adjustment I make affects all the velocities similarly and then power charges that are 1-2 grains away from the point I chose to adjust to, do not adjust accordingly. I get that the burn rate changes with load density etc, but should that not be accounted for in QuickLoad?

So I have been looking for a way to adjust something(s) that would make "all" data points match up to tested velocities.

When you match the velocity by tweaking the burn rate, do the back calculation in QL for each velocity of each round you shot. Then back calculate trial and error the Ba that history matches each velocity at different charge weights, then average those back calculated Ba
numbers to get an average Ba across those velocities. Use that avg. burn rate to forecast your next load.

Depending on how many charge weights you go up and the magnitude of each increment you may want to narrow down the range of the data you focus on to do this, because Burn Rate is not constant, using an average Ba you history matched at 87 to 90 gr. of powder probably doesnt work well at 81 to 83 gr of powder. You have to use a Ba that fits best with the data range you want to model.....Also if you do this at 70 degrees F and then go shoot in 95 degrees F guess what?
It wont work because Ba is not a constant.

Be sure to pay close attention to data ranges and temps in the model

 

[JKPhoto]

That is one of your issues if you are using the default cartridge value in the pulldown. You need to measure your actual fired/trimmed brass for that value. For example in win 308, there can be a 3 grain difference in H2o capacity between lake city and lapua or winchester brass. QL doesn't know what you are using for brass. You need to tell it by measuring the h20.

I agree ... in my case, for 300 PRC ...

QuickLoad used as a default
Before the recent update I think it was 99.50gr,
After most current update 94.50 gr H2O ...
My measurements:
ADG Virgin Brass: 93.67gr
LAPUA Virgin Brass: 94.76gr
LAPUA 1X Brass: 95.45gr

 

[Tripodmvr7]

Essentials :-

1. Select calibre and bullet type. Change bullet length if different from actual measured.
2. Change barrel length to measured from cocked bolt to muzzle tip (ignore muzzle brakes)
3. Measure case capacity and enter.
4. Enter COL as used - from tip of bullet to base - this measurement is used to calculate case fill

Add charge used and speed obtained. Add about 10fps for chrony at 5m.

A. Change BRF (Ba) to get speed measured. Once done I save this info so as to use it in future.
B. Get a copy of an OBT excel calculator and input the barrel length.
C. Adjust the charge to obtain the same barrel time as that reflected in the OBT calculation.
D. Load this charge and same COL and test run three or more bullets to see grouping. Get speed again as check.
E. Refine around this charge that gives a good group. Move up and down with 0,2 or 0,1 increments.

As can be seen this is a fairly uncomplicated procedure. My tally stands at more than 1500 calcs that have been 95% successful.

 

[Salmotrutta]

Mr. Slamotrutta, I have to ask you, why to do you tweak the case capacity to calibrate the load? That is the one thing that is easily measured and verified? In Mr. Long's paper, one of his suggestions to calibrate the load is to modify the bullet weight slightly. I don't understand that either. If you know the bullet weight and the bore diameter and case capacity why would you fudge them? None of those variables change with temperature to any great extent that would be measurable. On the other hand, Ba (Powder Burn Rate), is temperature dependent and varies powder lot to powder lot. So what difference does it make if you vary it +/_5% to get the load and the measured velocity at temperature to match. Starting Pressure, can be jump dependent depending upon whether the bullet is jammed or has clearance but it should be constant for that bullet in that gun. I have seen one equation where the initial starting pressure is dropped by so many psi for every two or three thousandths off of the lands the bullets are seated. I don't think that equation was verified by actual pressure barrel measurements in a ballistic lab. Just like too many cooks spoil the broth, too many variables cloud the results!

Thank you for your insights.

I have to admit it wasn't my idea. That came from the ballistician at western and was identified as the primary variable they used to tune QL and then verified the results via pressure barrel. The logic from them was that there are so many variables in chamber dimensions, throating, primer type etc. That can affect the models result that are not explicit variables, that the easiest way to account for those was to adjust case volume. Shot start/initiation pressure was useful to to adjust the model for bullet jump, bullet dimensions, hardness, etc.

By adjusting the Ba you are in affect influencing the model as well. To me it is useful to modify case volumes as I can easily see how far off of reality I am flexing my model (for me 5% is too far) and leads me to validate all my other input to make sure I don't have an error somewhere else. If I tweek a variable like Ba, I don't have context for it, and I think it's possible to "turn that dial" so far that you might cover up other errors w/o realizing it. It's just my process, not saying it's any better that anyone else's. I just tried to be clear on what I do, and where it came from.

I haven't tried your seating depth rule, but it sounds like a good place to start. I would assume that different bullets and throating greatly effect this.

 

[Veteran]

I have to admit it wasn't my idea. That came from the ballistician at western and was identified as the primary variable they used to tune QL and then verified the results via pressure barrel. The logic from them was that there are so many variables in chamber dimensions, throating, primer type etc. That can affect the models result that are not explicit variables, that the easiest way to account for those was to adjust case volume. Shot start/initiation pressure was useful to to adjust the model for bullet jump, bullet dimensions, hardness, etc.

By adjusting the Ba you are in affect influencing the model as well. To me it is useful to modify case volumes as I can easily see how far off of reality I am flexing my model (for me 5% is too far) and leads me to validate all my other input to make sure I don't have an error somewhere else. If I tweek a variable like Ba, I don't have context for it, and I think it's possible to "turn that dial" so far that you might cover up other errors w/o realizing it. It's just my process, not saying it's any better that anyone else's. I just tried to be clear on what I do, and where it came from.

I haven't tried your seating depth rule, but it sounds like a good place to start. I would assume that different bullets and throating greatly effect this.

You dont just tweak Ba in a vacuum. You home in on it w trial and error history matching to actual velocity measured by shot. When you adjust Ba it is only to output the actual you measured.

If you must adjust case volume I would keep it within 1 to 2% of what you actually measured when you weighed water vol.

 

[Veteran]

I would add, if you have to adjust Ba more than say 10 to 15% to get velocity matches you need to look at every assumption in your model then, something else may be off.

But between changing powder lots, humidity, or storage temp and humidity issues w your powder, having to change Ba more than 10 to 15% to match velocity says case vol,, bbl length, or something else is off.

 

[muzzletalk]

I would add, if you have to adjust Ba more than say 10 to 15% to get velocity matches you need to look at every assumption in your model then, something else may be off.

But between changing powder lots, humidity, or storage temp and humidity issues w your powder, having to change Ba more than 10 to 15% to match velocity says case vol,, bbl length, or something else is off.

That "something" most of the time can be manipulated with the "Weighting Factor". By default, it is .5. In many cases, mine ends up being .4xx.

 

[sfdoc2000]

What do you mean change the slope of the velocities?

Are you saying that when you run quickload at different charge weights and then graph the velocity vs. charge weight curve it is not a straight line? If that's what your saying, then the answer is because Burn Rate is not a constant with increasing fill capacity and change in powder pack density of the cartridge, and therefore pressure and therefore velocity will not be constant in terms of fps per grain of charge weight either.

You may be trying to fool nature? Can't Be done......though lots try it......especially these days in so many upside down ways......

As a caveat to what Veteran says about burn rates, I have found that the Ba of every powder (I have used so far) consistently increases with increasing chamber pressure and temperature. The Ba listed by QL is only an average of many different load combinations but needs to be tuned to your particular load. like always start in the midrange and work up knowing that you will probably need to increase the Ba with increasing loads to model the real world performance of each load.

 

[Veteran]

It depends on load density, percent fill, the powder stick or ball, and then temp and press too.

I've observed Ba drop with higher fill volumes and increased density w constant temp but of course pressure will act to increase Ba,
but load pack may decrease it. It all depends on the loads, load ranges, bullet seating depth, kinds of powder, etc. I have seen Ba trend down at higher charge weights too. In general we expect Ba and Velocity to go up with charge weight, but then it does not sometimes, as in the Satterlee Curve Flat spots for example. If velocity is flat or even trending down that implied Ba is flat or dropping even with increased charge weight too. A diminishing returns caused by pack of the powder, its shape and density, etc.
I also think harmonics may play into this behaviour too because of pressure and friction variation in the barrel but that's the subject of a whole different thread.

 

[Veteran]

That "something" most of the time can be manipulated with the "Weighting Factor". By default, it is .5. In many cases, mine ends up being .4xx.

I normally have my weighting factor set at .52 because shooting some compressed loads, and shooting loads with mostly greater than 93% case vol. fill, I believe some of my powder, especially the big chunky VV N series stick powders do not completely combust until a bit later in the process and follow the bullet at least a bit down the barrel.

From the QL users manual, 50% of the propellant mass is considered to move with the bullet. For typical cartridges, this is a good figure with which to work, so long as nothing better is available. I'm assuming a little more moves with the bullet , ie, 52% as described above. If you are shooting medium to low velocity charges at less than 90% case fill and using ball powders, maybe
it is down in the 40-50% range.

Weighing factor: # Input, represents energy losses from friction, heating and gas leakage; (Default is an estimated value based upon consideration of various cartridge parameters.) Most data records contain a 0.5. This means that 50% of the propellant mass is considered to move with the bullet. For typical cartridges, this is a good figure with which to work, so long as nothing better is available. Refer to the associated Bubble-help (tool tip) window for more information. When using so-called solid bullets, like Winchester FailSafeô, MEN-SFô, SFS, Hirtenberger ABCô or Barnes Xô, the user can set this value slightly higher (add 0.05). With moly-coated bullets (like NECO-Coatô processed) reduce this value about 0.02. Note that frictional loss percentage probably varies with jacket materials and barrel materials and bore profiles and this value is not constant along the path of the bullet through the bore. Nevertheless, in the current QuickLOAD version, a mean value of friction is assumed.

 

[RidgeTop]

what number are you using in the "weighting factor " ?

give these a try ;
264 win mag , .39
7 rem mag , .38


we would also need the COAL , BBL length ,

What is a 'weighting factor' ?