Lee Pro Auto-Disk; a better way

[berettaprofessor]

As I was looking through my reloading log, it occurred to me that I could use the data to make a better way to choose a Lee Pro Auto-Disk cavity size for a given load than the volume measure density chart supplied by Lee. I simply charted out a number of loads where I had used a specific cavity and obtained a charge weight to get a chart like that below, demonstrating that charge weight and volume is a linear relationship:

Best of all, you can use the trendlines and equation functions in Excel to get an equation and predict any cavity necessary for that powder. The formula for CFE Pistol, listed on the chart above, is y=13.812x -0.3323. If I knew I wanted a CFE Pistol load of 6.2 grains, for instance, I could simply plug that into the equation above as "y", making the predicted cavity needed, or "x", = 0.473. Yes, I know that there is no 0.47 Lee cavity on any disk, but now I know that the 0.46 cavity will be as close as I can get.

The equation for W231, for those who want it, is y=11.467X -0.2417.

Now I'm left wondering why Lee doesn't just provide these linear equations, instead of the volume measure density figures that never seem to be accurate enough to give me the right cavity first.

 

[Stripesdude]

I get the same thing when trying to use the chart - their chart is useless. The cavities never end up with the charge weights they claim.

The linear trend equation is a great approach. And I have two sets of disks - one with screw holes tapped into the side of each cavity. That way I can turn a screw in or out to fine tune the cavity size.

 

[Hokie_PhD]

Cool
Thanks for this I'm going to try this but have no reason to doubt you

As for your question my guess would be liability. They probably had a lawyer tell them they can't release info for who knows what reason.

 

[Wreck-n-Crew]

Seems like it would be a lot more handy if it weren't so time consuming to get an actual VMD for each powder to begin with because Lee's volume measurements are not on par otherwise one could simply transfer the whole chart to Excel and have quick access. Since they are not one would have to generate accurate volume data which one would need to complete a full VMD Excel sheet that does the calculations.

Actually it goes beyond the need for just the pro-disk since other measures use volume people also depend on the Lee VMD to get started. If we had some accurate numbers from experience and verified close then one could build an Excel chart for VMD that would be quite handy. I can contribute some measurements myself to help but I have a feeling if we employed others (self included) this would become a sticky thread quickly. I may make one myself.

I like it, Thumbs up!

 

[Tilos]

I have found when using the Lee VMD chart to pick a disc, it always comes up light or less than the weight charted.
I try and thro 10 charges into a larger case to weigh, as it gives me an average.
Like having a target weight of 4.3 gr, I'll thro 10 (10x4.3= 43gr) and set the scale at 43 gr.
My "long" 45 case (top)
My "long 9mm case"(clear tube)

I usually end up using the next bigger disc cavity from what the chart states to get the closest to the target weight.

 

[Wreck-n-Crew]

I have found when using the Lee VMD chart to pick a disc, it always comes up light or less than the weight charted.
I try and thro 10 charges into a larger case to weigh, as it gives me an average.
Like having a target weight of 4.3 gr, I'll thro 10 (10x4.3= 43gr) and set the scale at 43 gr.
My "long" 45 case (top)
My "long 9mm case"(clear tube)
View attachment 230307
I usually end up using the next bigger disc cavity from what the chart states to get the closest to the target weight.

Good idea. beats dumping several charges from a single case into a pan. Could remove the springs or chain on actuated dispensers too if someone was up to it.

 

[Ole Joe Clark]

I use the diameters that throw the charge weight that I want and log the information. I also drill out the useless diameters to something I can use. I recently did a little calculating and guesstimating for a diameter that would drop 5.3 gr Unique. Drilled it out and it drops the charge as desired.

Have a blessed day,

Leon

 

[Mauser69]

Frankly, I do not understand the fuss. I have absolutely NO issues with the VMD charts provided by Lee.

Yes, the exact weight for any specific powder/cavity is almost never "exactly" what the chart says, but so what? That chart is perfect to get you started. When I am looking at a new load, I always weigh the charge given by the suggested cavity, then one either higher or lower, depending on where the first one landed vs my target weight.. Using a chart with a line on it would change absolutely NOTHING in this process. If anything, it would make it more difficult: first, I would have to find the correct chart for the specific powder (vs just picking up a single piece of paper with ALL powders shown in the same place), then I would have to take the time to trace out two lines to get the actual cavity suggestion from the intersect point. While that may not be terribly hard, it is still worse than simply looking over a list of numbers to find the one closest to my target charge.

And then when I decide on the one to use, my log is annotated with the exact weight and the cavity used. If I want to repeat that specific load, there is no guessing or testing involved - I just set up that same cavity. But I do re-weigh the charges thrown for that loading session, and you know what? The actual weights thrown are RARELY identical to the last use of the same powder/cavity - they are always very close, but not the same. And this is to be expected, since you cannot control for the variables like temperature, humidity, and powder lots.

 

[berettaprofessor]

Using a chart with a line on it would change absolutely NOTHING in this process. If anything, it would make it more difficult: first, I would have to find the correct chart for the specific powder (vs just picking up a single piece of paper with ALL powders shown in the same place), then I would have to take the time to trace out two lines to get the actual cavity suggestion from the intersect point. While that may not be terribly hard, it is still worse than simply looking over a list of numbers to find the one closest to my target charge

Actually, with the equation, you don't need a chart at all. Simply y=mx+b linear equation solving. My point is that it gives me a starting cavity MUCH closer than the VMD chart calculations, which, as noted by others, almost always underestimates the cavity needed.

 

[wally]

I have found when using the Lee VMD chart to pick a disc, it always comes up light or less than the weight charted.

Can you blame them? You know somewhere out there some guy is going to pick a powder and load, choose a disk and just load and shoot it without verifying the actual charge thrown!

 

[Rule3]

How does all the calculation take into account the different density of all the different lot numbers of powder. Along with humidity altitude etc.??

Same as the Lee chart.It was close enough. OK that is to high, try the next lower.
My can of HP38 is not going to be the same as yours or theirs.

Over time I simpley wrote my own chart on the powder and disc number I was using. Really only need a few for each powder, I don;t need to know 15 grains of HP 38 or similar

Those days are gone now anyway with the Lee Auto Drum

 

[RandyP]

I only use Win 231/HP-38 for all my handgun reloads so it was pretty simple to spend maybe an hour or two and run test throws of 10 each for the various holes in my disks and record them on a chart I keep on the wall by the press. I will of course still verify the actual weight thrown with each caliber setup.

 

[LiveLife]

How does all the calculation take into account the different density of all the different lot numbers of powder. Along with humidity altitude etc.??

My can of HP38 is not going to be the same as yours or theirs.

I forever resolved the Pro Auto Disk fixed hole issue with $1 brass screw modification - https://www.thehighroad.org/index.php?threads/working-diy-micro-auto-disk.741988/

Now, I have the ability to adjust powder drops in .1 gr increments and be able to drop precisely 5.0 gr of W231/HP-38 when the fixed holes are off by .2-.3 gr. And once I make the adjustment for my bottle of powder, the drops will be consistent until the bottle is empty.

Added bonus is I can meter W231/HP-38 consistently down to 2.0 gr and Bullseye down to 1.5 gr and be able to adjust up in .1 gr increments. I don't know of many powder measures that can do that.

 

[1KPerDay]

I just write down what the disc actually throws with each powder I use. Some powders throw right on what the chart says, some are way off. I always weigh a few charges anyway.

 

[Gottcha]

There is a chart that tells you what hole to use?!

 

[LiveLife]

There is a chart that tells you what hole to use?!

Many members found that depending on the powder type (flake vs ball), lot number, age of powder (powder will weigh lighter as volatile component evaporates), and ambient humidity, actual powder charges dropped and weighed could be off significantly from the chart by .2-.3 gr.

 

[Tilos]

Good idea. beats dumping several charges from a single case into a pan. Could remove the springs or chain on actuated dispensers too if someone was up to it.

I make the "long" case to fit under the dies when the shell plate is down.
I use the chain arm on the Auto Disc, but NOT the chain, a spring from that arm to a lip under the die head.
Spring setup:

This allows me to hold the long case under the expansion die with one hand, actuating the powder drop with the other, and follow the expander die core up and down for 10 drops with the long case.
Weighing 10 drops and averaging will give a better measurement of what a cavity is actually dropping.
I find the oem wrap around spring setup too stiff to operate the powder measure by hand.

 

[Wreck-n-Crew]

There's one problem I'm finding with the calculations using volume and I suspect that some others have encountered it as well. I need another UNKOWN value to me in order for predictability.

Case in point: I used CC to measure an uncharted volume on the VMD chart for Autocomp powder. (maybe there's an update but I didn't have it going in). I used a volume of .44cc that produced a charge weight of 4.5 grains on average and very consistently I might say. Autocomp meters very well in that manor. Based on that if compaction wasn't a factor a simple VMD could be established...however compaction is and that compaction factor will vary by powder for all the reasons well known to most of us such as grain size, weight, and shape for example. As volume goes up so does the Percentage of compaction and percentage of weight by volume.

Moving on I measured an unknown to me charge using .7cc producing 9.4gr average. IF VMD were as simple as XY=z then X being desired charge times VMD would yield a CC volume of .9165cc no where near .7cc results of 9.4gr and closer to 6.9 gr by calculation. It gets worse. Using a 3.4 CC volume average weight was 46.7. Where if using the first actual volume as the indicator to the missing number in the equation the solution is wrong. The solution is going to be wrong without a variable of compaction based on volume for each powder which also varies. Now having a second Measurement to plot a chart with predictability calculations may or may not prove fruitful. Maybe a 3 point or more would improve predictability but those must be weighed and tested. There is no way a standard VMD can be the only factor in order to be hitting the mark with a decent degree of predictability if the powder is used for a wide range of calibers and charge weights.

Based on the original measurement the VMD would be .09777777xx producing a charge of 34gr but the actual volume is 46.7 (avg). a difference of 12.7 gr and in the neighborhood of %25 increase. Granted Autocomp is not going to be charging anything with such large charge weights but unique for example will vary from around 4 gr in a light pistol load to 31gr for a 10gauge. Different powder type, weight, shape but compaction is definitely going to be a factor in how much the weight will change using a VMD calculation based on volume.

I have some Unique and ill do a comparison when I get back home as I've run out of free time at the moment and need o get going. Update everyone later.....

 

[Wreck-n-Crew]

There is a chart that tells you what hole to use?!

Lee VMD chart uses a measurement of volume that can be calculated to predict CC volume. Based on the CC volume calculation you use the closest whole size in an Autodisk to get started. But it's off in all the cases I've seen and as eluded to in my post#18 there is a reason why it can't be done with real accuracy without another variable in the equation to represent Compaction by increased volume and based on the powder and powder type. As far as I know it doesn't exist....not to say there is not a way to get there. It just won't happen with a simple calculation of VMD X charge weight = CC.

 

[kingmt]

Thanks for sharing your helpful tips. I'm sure there are some that will find it useful. The nay crowd can just look for their own way of doing things.

 

[Rule3]

I just write down what the disc actually throws with each powder I use. Some powders throw right on what the chart says, some are way off. I always weigh a few charges anyway.

To simple!

No powder for you! Back of the line!

 

[Rule3]

I have my chart listed for any normal loads and what discs for

Longshot
Power Pistol
Unique
Bullseye
HP 38
Win Auto Comp
2400
H110
HS6

Rifle powders I weigh out and then go from there.

So any grain in a normal load I can tell you what disc hole (with my powders and humidity)


AS MENTIONED, THE LEE CHART IS SOMETIMES ALMOST EXACT, OTHERS IT IS SO FAR OFF IT'S DANGEROUS.

 

[Zendude]

I have to go up two sizes for Unique. One for everything else.

 

[Gottcha]

Lee VMD chart uses a measurement of volume that can be calculated to predict CC volume. Based on the CC volume calculation you use the closest whole size in an Autodisk to get started. But it's off in all the cases I've seen and as eluded to in my post#18 there is a reason why it can't be done with real accuracy without another variable in the equation to represent Compaction by increased volume and based on the powder and powder type. As far as I know it doesn't exist....not to say there is not a way to get there. It just won't happen with a simple calculation of VMD X charge weight = CC.

It is very off at least with CFE pistol powder. I also wrote down what size disk throws throws a specific charge. Then I bought the Lee charge bar(what I call it) to help me dial in what I want.

 

[bluetopper]

Yes....Lee Auto Pro Disc.....any other way is a better way.