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How Does The Chargemaster Do That?

CharlieNC

Gold $$ Contributor
Using the CM for a while on non-critical loads, I began to increase my cross-checks on a more sensitive scale. If all goes well the CM is within +/- 0.03gr, much tighter than the 0.1 resolution. How?
Using the more sensitive scale, I increased a load by 0.01 increments; weighing them on the CM I observed the reading did not change until a full 0.1 increase occurred. Meaning it truncates to the lower 0.1 gr, not rounding. This means during the incremental trickling/weighing stage it will not decide to stop until the full 0.1 programmed value is achieved vs stopping based on a rougher round off value. It also means it it overshoots by a few .01's then it doesn't care until a full 0.1 error occurs.

The most critical requirement to achieve uniform loads lies in achieving very fine charge increments during trickling. If you observe the last trickles, as long as these are typically small with no clumps of inadvertant vibration then the uniformity is much better than maybe expected. If the charging stops suddenly, probably vibration yielded a false reading and an undercharge occurred; but unfortunately an error will not be displayed because it though the false reading was correct.

Adjust to achieve very fine trickling; the uniformity is no better than the trickling increment. No vibration, watch for clumpling, and you should achieve excellent uniformity.
 
My own testing revealed many loads that the scale said were "right on" were actually low. In that case, one would think the dispenser should just keep on dispensing.

Observation led me to believe a final "trickle" of powder would fall with some velocity, making it register momentarily heavier than its actual weight.

Dispensing would stop and the scale would read exactly the target weight. But the weight of the powder in the pan could be significantly lower than target when checked on an A&D FX120i.

Changing parameter S_S from 128 (factory setting) to 255 allowed the scale 255ms (max possible) to settle down before the microprocessor considers the scale's weight final.

This change, along with slowing the final trickle speed down as far as possible, slightly improved my Chargemaster's overall performance. It also shifted the distribution of my Chargemaster's throws from slightly more lower than target to slightly more higher than target. And IMO that is where it should be.
 
I increased a load by 0.01 increments; weighing them on the CM I observed the reading did not change until a full 0.1 increase occurred.
What powder are you using that is .01gr per kernel?
There is filtering/stabilization of scale measure in most scale programs.
The ChargeMaster stops in combination of rate change and proximity to set charge. So as you're finding, you can creep into single kernel accuracy, even while the scale will not show this resolution.
I operate mine in a manner that stops on the closest powder kernel. But I can also detect when this condition is not met, even without watching actual charging, by observing scale settle after disturbance.

Always touch the pan after dispensing to get a re-read. If it doesn't lock right back into desired charge, with nearly no settle, it's a suspect charge. Just dump & dispense another. It happens like this here & there, no big deal.
 
What powder are you using that is .01gr per kernel?
There is filtering/stabilization of scale measure in most scale programs.
The ChargeMaster stops in combination of rate change and proximity to set charge. So as you're finding, you can creep into single kernel accuracy, even while the scale will not show this resolution.
I operate mine in a manner that stops on the closest powder kernel. But I can also detect when this condition is not met, even without watching actual charging, by observing scale settle after disturbance.

Always touch the pan after dispensing to get a re-read. If it doesn't lock right back into desired charge, with nearly no settle, it's a suspect charge. Just dump & dispense another. It happens like this here & there, no big deal.

Used CFE223. For critical applications I re-weigh on another scale that has .01gr resolution, only takes about 3 seconds to get that extra assurance. Like you said, it's nearly always apparent when a problem occurred.
 
For a time, I verified CM dispenses with an Acculab. This helped me learn and modify my CM.
What enabled me to drop kernels at a rate best suited to sampling is separate slowing of motor jogging. I did this with a potentiometer inline with the motor, adjusted to cal with each powder.
Once I got a feel for good -vs- bad in this, a more accurate scale was no longer needed.
After all, with single kernels falling every ~4-5sec, the dispensing program will settle on one of them. That's as accurate as we will get regardless of scale.
CMmodsSM.jpg
 
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. . . What enabled me to drop kernels at a rate best suited to sampling is separate slowing of motor jogging. I did this with a potentiometer inline with the motor, adjusted to cal with each powder.. . . After all, with single kernels falling every ~4-5sec, the dispensing program will settle on one of them.
That's a great mod if one can do it . . . you just can't slow down the final trickle speed enough reprogramming the parameter alone.

How long does it take you to dispense (eg) a 50gr charge?
 
I loaded with two Chargemasters for several years. Did some tweaking to the programing and used the straw mod for a while. Then I got bolder on the tweaking and went to the bushings that MDM sells on the forum. They work pretty well still but I have a new system that is faster and more accurate, I now drop charges with a Uniflow and trickle up with a Dandy Omega trickled. Weight is checked on an A&D FX120i scale. I haven't used the CMs in a few months now.
 
There are a couple dozen parameters that decide what's acceptable and when to stop.

I adjust the first 3 to suit the powder type and amount I'm working with, along with controlling the straw in-feed opening size gives me very acceptable accuracy.

Didn't some fella some years ago set a 600 yard group size record using powder dispensed from a ChargeMaster 1500 ?
 
For a time, I verified CM dispenses with an Acculab. This helped me learn and modify my CM.
What enabled me to drop kernels at a rate best suited to sampling is separate slowing of motor jogging. I did this with a potentiometer inline with the motor, adjusted to cal with each powder.
Once I got a feel for good -vs- bad in this, a more accurate scale was no longer needed.
After all, with single kernels falling every ~4-5sec, the dispensing program will settle on one of them. That's as accurate as we will get regardless of scale.
View attachment 1018556

Nice setup!! I am surprised how well the scale operates, including the "software"; mine has never drifted at all. May take a bold step and load for Fclass instead of the beam.
 
ScaleMod2SM.jpg
That's a great mod if one can do it . . . you just can't slow down the final trickle speed enough reprogramming the parameter alone. How long does it take you to dispense (eg) a 50gr charge?
I use a 10-turn, 10ohm pot. It does not seem to affect full speed dispensing, and barely mid speed. But I can affect slowest trickle speed from full to stop.

With that I'm adding ~15-30sec of trickle time for each dispense.
Then I disturb the pan and watch the settle(~5sec). If bad, I dump the charge & dispense again. If good, I slowly pour the powder from pan to funnel/drop tube for consistent charge density(~30sec). Then I set the pan back on the scale, watch it settle to zero, re-zero or not, hit dispense, and seat a bullet in the case I just charged.

Takes time, not a race.
As well I have my processes in priming to crush, shoulder bumping, neck sizing/matching tension, seating to qualified CBTO, etc. Just not a fast reloader..
 
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True. It would help if more info was available from vendors, instead of needing to figure out.

My sentiments as well.
I am new to the device; have thrown about 400 charges.
A small percentage were within spec ( 0.10 gn +/-).
With a set point -0.20gn below finished charge, most were close enough to take time to trickle up.
But too high a percentage were over-thrown to make it an efficient device.
From the go I have been using the brass insert, a Tripp line conditioner, and every computer, wifi, fluorescent, TV, and anything else I could unplug, in the house shut down
I recently stumbled onto the blog suggesting the 1st 3 parameter changes, but have yet to try it with those changes made
It seems odd that if there are critical adjustments to be made, there is nothing in the instructions.

Reading the manufacturer's literature (i.e. Lack of detailed detailed instructions) suggests this to be a plug-and-play device.
Clearly it is not

That said, Where can one learn to
'Swing the hammer'?
Thanks.
 
For a time, I verified CM dispenses with an Acculab. This helped me learn and modify my CM.
What enabled me to drop kernels at a rate best suited to sampling is separate slowing of motor jogging. I did this with a potentiometer inline with the motor, adjusted to cal with each powder.
Once I got a feel for good -vs- bad in this, a more accurate scale was no longer needed.
After all, with single kernels falling every ~4-5sec, the dispensing program will settle on one of them. That's as accurate as we will get regardless of scale.
View attachment 1018556

I just checked my Chargemaster, it doesn't have the adjustment screw, no ability to modify speed of disbursement.
 
View attachment 1018578 I use a 10-turn, 10ohm pot. It does not seem to affect full speed dispensing, and barely mid speed. But I can affect slowest trickle speed from full to stop.

With that I'm adding ~15-30sec of trickle time for each dispense.
Then I disturb the pan and watch the settle(~5sec). If bad, I dump the charge & dispense again. If good, I slowly pour the powder from pan to funnel/drop tube for consistent charge density(~30sec). Then I set the pan back on the scale, watch it settle to zero, re-zero or not, hit dispense, and seat a bullet in the case I just charged.

Takes time, not a race.
As well I have my processes in priming to crush, shoulder bumping, neck sizing/matching tension, seating to qualified CBTO, etc. Just not a fast reloader..

 
@ED3 there are a number of threads on parameter adjustments, and these are very effective. You can run the first stage longer to achieve speed, but then be sure that the third trickling stage is activated at least 0.3gr before final to achieve precise trickling. Take a little time to experiment with these to find out what works best for your powders.
 
Filled 163 cases with 217 grains of H50BMG last week, I use the Chargemaster to dump first load, then unto the Sartorius to confirm, and trickle to final with a Dandy trickler.. Equipment had all day to warm up. . The CM would throw just about every charge a little light ( Range was generally 217.314 to 217.370 ) It hit this CONSISTENTLY , where I would generally have to dump 2, maybe 3 grains of powder to get to final weight. I was very surprised at how accurate it repeated the charge.
 
I think we should demand RCBS install one of these for everyone!
Well, if they were really smart they would have let the programming parameters alone do the job . . . but they didn't.

They would have been smart to allow the user to enter the approx weight of a granule of powder. Said another way, they should have allowed the user to set the tolerance around the target. When you have a powder like N570 that can weigh 0.4 to 0.7gr per granule, you can't use the same tolerance you would use for HP38.

They would have done better had they allowed more than 0.25 seconds during trickle to wait for the strain gauge scale to settle down.

But overall they did pretty well balancing speed, repeatability, and price using a strain gauge scale.
 

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