RCBS charge master vs lab scale?

[bllistc]

So I’ve been reloading for a while but kinda new to the precision rifle game. I’ve seen a couple threads talking about the RCBS chargemaster and wanted to know how it compares to measuring manually using a lab scale sensitive to 1mg (about 0.015gr).

Any thoughts or recommendations?

 

[dirthead1]

I have used a Charge Master for years and recently purchased a Sartorius Entris64. Over the past few days I've loaded 200 rounds of 6.5 Creedmoor. My load is 41.2 grains of RL16. I set the CM to throw 41.2, then check on the Sartorius and add/subtract to get the weight from 41.180 to 41.210. That range is about the weight of one kernel of RL16 (.030 grains). What I've found is that with the CM, 5 of 10 charges will be fairly close (within .05-.07 grains), 3 of 10 will be around .1 over/under, and 2 of 10 will be .2 to .3 grains over/under. Occasionally I'll get one that is .4 over. Using the CM only, my SD has been running 8-10 with this or other loads (which isn't terrible), but never lower. Using the Sartorius, my SD is down to 4.8 and ES is around 17 fps measured over 30 rounds. So yes there is a big difference in accuracy and consistency from load to load. Now I'm confident that the charge weight of every round is within the weight of 1 kernel of powder.

Now whether or not that makes a real world difference on target is a different question. I guess it depends on what you are shooting at and how far away it is.

 

[bllistc]

Gotcha. Thanks for the info.

 

[paraiso100]

My chargemaster is apparently more consistent than dirthead1's. I have the CM and an fx120i. My CM rarely throws outside of a .1 grain window. About once every 50 charges thrown the CM will show 39.7, and the fx120 will show an error of more than .1 grain either way. I see very little difference in my SDs and ES between the scales, but I'm in a good node. I am at an SD of 7 with a 6xc.

With the fx120i/auto-throw I got scale stability and speed. These were what I was looking for as I never had a problem with SD/ES with the chargemaster.

 

[918v]

Electric scales are temp sensitive. One person may see a very small ES while another see huge ES, difference being the former is operating under ideal conditions and the later not so much.

 

[Muley Buck]

Electric scales are temp sensitive. One person may see a very small ES while another see huge ES, difference being the former is operating under ideal conditions and the later not so much.

What exactly are the ideal conditions you are referring to?

 

[918v]

For my scale it’s 70 degrees. Outside of that it tends to drift. But then again it’s resolution is to the 4th decimal point. What I’m trying to say is that if one guy is using his scale in the garage when it’s hot or cold, and another guy is using his scale inside his air conditioned house they will have different opinions on their scales accuracy. Then there are manufacturer tolerances...

 

[Muley Buck]

For my scale it’s 70 degrees. Outside of that it tends to drift. But then again it’s resolution is to the 4th decimal point. What I’m trying to say is that if one guy is using his scale in the garage when it’s hot or cold, and another guy is using his scale inside his air conditioned house they will have different opinions on their scales accuracy. Then there are manufacturer tolerances...

Ok, gotcha. Thanx for the clarification.

 

[_Raining]

For my scale it’s 70 degrees. Outside of that it tends to drift. But then again it’s resolution is to the 4th decimal point. What I’m trying to say is that if one guy is using his scale in the garage when it’s hot or cold, and another guy is using his scale inside his air conditioned house they will have different opinions on their scales accuracy. Then there are manufacturer tolerances...

People also report issues with needing line conditioners to have a stable environment. Me personally with my entris and being in a shitty apartment, if I shift my weight in my chair the scale will change value. If I stand still then it stays still, which is how I know it isn't the outlet. I also found a spot in the apartment that is more stable and I can walk around and not have the scale move. The kitchen counter sort of sticks out on a peninsula and if the scale is on there I get up to .2 grains movement when walking around but if I move the scale to the part of the counter where the 2 walls meet then it is perfectly stable (same outlet used). Also, a draft in the air can change the reading on the scale. One person may not let the scale warm up etc.

tl;dr A lot of things effect scales.

 

[canezach]

I think another thing to consider with the Chargemaster is reprogramming and inserts. In my experience, once I reprogrammed the Chargemaster and added the brass inserts (I have the standard brass insert with the smaller insert as well), I reduced the number of overthrows, but what's really happening is the Chargemaster is slowing down earlier and the insert isn't allowing as much powder to be dispensed at one time, so the scale isn't stalling because you just threw 8 kernels onto the tray in half a second.

 

[John Glidewell]

Electric scales are temp sensitive. One person may see a very small ES while another see huge ES, difference being the former is operating under ideal conditions and the later not so much.

Yes, temp, humidity, air flow, static electricity....all play havoc with electronic scales. I moved indoors to controlled environment, much better results on range. 68-72, 35% humidity.

 

[towerofpower93]

Had/have a CM for a few years and it was better than throwing and trickling up, but even with the reprogramming and straw tricks I’d get overthrows.

Went to the auto trickle/auto thrower combo and not only is it more consistent, it’s faster; both from a raw ‘time from pan down to pan up’ but also in that I very rarely have to add or subtract powder.

I keep a .02 standard, which is basically a kernel of any of the longer stick powders. If I set it for 70.00gr, I’ll take 69.98-70.02, as taking out or putting in a single kernel can cause the high to swing to the low and vice versa.

 

[John Glidewell]

The Gempro 250 is still a strain gauge type scale. You will want to warm it up (leave it on) for at least one hour (2-3 is better) before you use it. I have it and it is a good scale, but still a strain gauge scale. Here is a good video about the 2 different types.

helps to understand the difference in scales too. The CM would be a Strain gauge type scale.

 

[SporterII]

Chargemaster is a great and fast measuring cup. That's how I use mine.

 

[BigTex]

I use a CM exclusively, I used to double weigh on a GemPro 250, but found it to be a waste of time. My loads are very consistent with low ES and SD and I shoot out to 2k with certain fairly regularly. I think other variables (i.e. neck tension, bearing surface length, case volume, etc) have enough effect to make a <0.1gr delta in powder weight to disappear in the ether. My CM is always +/- 0.05gr on the GemPro.

 

[SporterII]

Knowing your equipment repeats reliably is key.