Scale Issues!?!

[msquared]

After carefully loading some test loads, weighing each charge, and chrono results coming out almost the same for each different load, I suspected something was wrong with either the chrono or my powder scale.

Another oddity is my loads are higher than what I hear from other people. Example 4.2g of titegroup pushing a 180g berrys bullet out of a G35 is giving me 873 ave fps for 163 PF.

SO i broke out the old beam scale and compared my RCBS 750 readings. What weighs out at 4.2 on the beam shows 4.7 on the RCBS.

Bottom line it appears my RCBS is usually higher but seems to jump around. I thought my dillon measure was moving on me but now i am wondering if it is my scale that has issues.

Frustrating to say the least. I am trying to work up a major load and cant seem to get anything to make sense. Wasted 30 minutes hand weighing 4 different loads to have them all chrono within 4FPS ave.

Anyone experienced this? Should i chuck it and replace it? If i cant trust it what good is it?

What are you guys having good luck with?

 

[shibumiseeker]

I don't trust electronic scales or cheap beam scales. I've seen too much variation.

My GF as part of her job has to weigh things that are three orders of magnitude smaller than what we weigh. So much so that someone walking in the hall outside the lab throws the reading off. Much more patience than I.

I don't worry too much as I'm usually keeping my charges well below maximum, but when I have approached maximum I will triple check the charge weights.

 

[ambushunter]

I have the 1500 combo and have had great sucsess with it. I turn mine on a couple hours before I plan on using it. It is on a very sturdy bench. For most my loads I don't recheck measurement. But in a couple rifles I do. The most it has been off is .2 grains. But this is weighing over 20 grains. I rezero the scale several times while reloading just to be safe. I don't trust beam scales, to much can affect there acuracy. Try cleaning it the best you can. And then throw a charge and weigh it 3 times.

 

[mhs]

After carefully loading some test loads, weighing each charge, and chrono results coming out almost the same for each different load, I suspected something was wrong with either the chrono or my powder scale.

Another oddity is my loads are higher than what I hear from other people. Example 4.2g of titegroup pushing a 180g berrys bullet out of a G35 is giving me 873 ave fps for 163 PF.

SO i broke out the old beam scale and compared my RCBS 750 readings. What weighs out at 4.2 on the beam shows 4.7 on the RCBS.

Bottom line it appears my RCBS is usually higher but seems to jump around. I thought my dillon measure was moving on me but now i am wondering if it is my scale that has issues.

Frustrating to say the least. I am trying to work up a major load and cant seem to get anything to make sense. Wasted 30 minutes hand weighing 4 different loads to have them all chrono within 4FPS ave.

Anyone experienced this? Should i chuck it and replace it? If i cant trust it what good is it?

What are you guys having good luck with?

Do you turn the scale on, let it warm up for 20 minutes or so, and then calibrate it? Many of the scales I've used have a fair amount of drift until they warm up. After they're warm, temperature changes, air currents (hvac vent?) and/or static can influence them.

 

[Iron22]

Make sure there are no drafts and the scale is on a very level surface

 

[msquared]

Thanks for the input.

Yes on the warm up. Its on AC power too not battery. No drafts, fans, windows etc. It is consitantly higher than my beam scale (which now makes senses compared to others loads).

I have emailed RCBS to see what my options are to repair it.

I am thinking at this point i will just be replacing it. Not sure with what yet. THe beam scale is sooooo slow compared to electronic.

 

[blainepoe]

Do you turn the scale on, let it warm up for 20 minutes or so, and then calibrate it? Many of the scales I've used have a fair amount of drift until they warm up. After they're warm, temperature changes, air currents (hvac vent?) and/or static can influence them.

I thought my Dillon was playing tricks on me then I realized it was the scale. Follow the above directions and weigh your calibration weights often to check the scale's accuracy. If your press is set right, you won't get much more than tenth grain variations.

Take it easy Mark.

 

[rj3438]

Sounds like a classic manufacturing type problem. Is the process not capable or is the measuring equipment not capable of detecting what the process is doing?

First step to answering this is to determine if the measuring system (your scale) is capable. If it is, then the capability of the powder dispensing method can be determined.

The way to determine measurement system capability is to do a Gage Repeatability and Reproducibility study. This involves taking a set of parts (or in this case powder charges) and measuring them multiple times. The data is then ran through some calculations and the results will tell you if you can trust the gage for the accuracy you require. In this case if you're the only one doing the measurements the reproducibility part would be ignored and only repeatability looked at.

If the gage is acceptable, next step would be to do a capability study on the dispensing method. This would just be measuring a number of consecutive charges (at least 30) and doing calculations on the weights. This would tell you what kind of variation you are getting from charge to charge.

If you want to do a gage study you can google for info on this or I can help you. We could define a setup, you take the measurements and send me the data and I can run it through my work software.

 

[BE Mike]

I would check the scale with check weights before I took any further action. I've owned a couple of very good quality electronic scales and they were always right on when I used check weights. The only scale that I ever had that was off, was a Lyman D-7 beam scale. It was off on lower weights, but accurate with larger weights, like bullets. I sent it back to Lyman and when it came back, it was accurate at lower weights, but off when weighing heavier items...go figure.

 

[SmileDocHill]

I don't reload so take this with a grain of salt. When I was taking micro analytical Chemistry we had very sensitive scales and when you took a substance out of a sealed container you could watch the "weight" of it change. In this case it was because the substance was stored in a sealed container that was last opened when the humidity was different, or the substance was isolated and not allowed to go from what you would normally call dry to real dry. When you put it on the scale you were watching the substance either "dry off" or absorb water from the air. We did an experiment early in the class just to understand the equipment we were using where we placed dry desiccant on the scale and watched it suck the humidity out of the air, and then at the end of a process where we isolated a substance he intentionally had someone not properly dry their resulting pile of powder and we watched it further dry on the scales. (by watching it I mean we watched the digital number on the scales either climb or decrease) I don't know how many significant digits the reloading scales use so this may be more an entertaining side note than anything.

 

[The Keymaster]

I have had a variety of electronic scales, and finally got to the point where the only alternative was to shell out some real money and buy a lab scale. I have been exceptionally pleased with the results. 10 minutes of warm up time is essential.

 

[msquared]

I received this reply from RCBS Tech Support! Fast response. I will report back if this resolves the issue...

"
you may have some static electricity build up or residual stress in the scale. Try wiping the scale down with a bounce dryer sheet or a static cloth to remove any built up electricity. Also try this: tap the platen until you get an "OL" for overload and then press zero, then tap the platen quickly 30 times with less pressure so that there is NOT an "OL", and then press zero again. Then you can calibrate the scale and it should be accurate. This "love tap" relieves the residual stresses inside the scale. Let us know if this doesn't work, have a great day."

 

[Cannondale]

Suggest that you use the Beam Scale, it is less prone to drift

 

[msquared]

Well the "Love Tap" procedure from RCBS Tech support worked! The scale now reads the same as my beam scale and a borrowed electronic.

 

[kolob10]

Ditto on the verification with a check weight of know weight. I once had a RCBS scale that was off .8 of a grain. I use a Ohaus (RCBS) 10-10 without any issues. I also have a Dillon electronic scale that has proven very accurate.