Do you trust your scales? Lee vs MTM DS-750 vs RCBS M500

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I posted this in another thread --

https://www.canadiangunnutz.com/forum/showthread.php/1530896-Reloading-scale-opinions

-- but that thread seems to have gone quiet. Sorry for the double post but I am curious to hear thoughts on what I am seeing with three scales that I have.

I have three scales and I'm wondering what to think when they don't all agree with each other or with what I "know" a weight should be.

I have

  • the Lee scale (my first scale when I just started reloading)
  • an MTM DS-750 (a digital scale picked up when my eyeballs fell out after reading the Lee scale for a few hours), and
  • an RCBS M500 (because I wanted an easier to read beam scale).

I also have some OHAUS Sto-A-Weigh calibration weights. Just playing around I will pick a random assortment of weights and try them on each of the scales. I'm limited of course by the smaller capactity of the Lee scale.

I am finding that the scales do not always agree with one another. And all of the scales are all multiple tenths of a grain away from what the weights should be when I do the gram-to-grain conversion mathematically.

I think my technique is OK and the scales seem to be stable. They are on a solid platform at eye level with no air vents or other interfering items. I have not modified or tuned the scale in any way.

Here's what I've observed with the three of them:

  • The Lee is a pain to zero but holds its zero once set. The vernier poise is a brilliant design in theory but it takes practice and really good light to read it.
  • The MTM is consistent and always returns the same values for its calibration weight and my various powder pans. My only worry with it is that it's a cheap digital scale.
  • The RCBS is very easy to zero but sometimes will not return to zero after weighing something. After zeroing it will return to zero after moving the beam by hand. But after weighing something it often will not return to zero. And rezeroing sometimes requires a LOT of turns of the adjustment wheel, making me think that the initial zero was not at all correct.
  • The Lee and MTM almost always agree with one another when weighing unknown weights. When they disagree they tend to be off by one tenth of a grain, with the MTM typically reading +0.1 grain higher than the Lee. I'm willing to accept that's due to me misreading the Lee scale or due to the digital scale rounding up when the Lee scale seems to indicate a measurement between tenths of a grain.
  • The RCBS often disagrees with the Lee and MTM scales when weighing unknown weights. And that disagreement can be by multiple tenths of a grain. The disagreement is enough that I would worry about it if I was weighing powder loads.
  • All of the scales are off when I convert the weight of the calibration weights from grams to grains. All of the scales are off by +0.2 to +0.5 grains, even when rounding the math is considered. I don't think this is due to contamination of the OHAUS weights but I guess it could be.
  • A test I did last night is really bugging me. Weighing a 32-20 case on all three scales, I get 66.7 grains on the MTM scale, 66.6 to 66.7 on the RCBS (which makes me think it's actually something like 66.65 grains) and 66.3 grains on the Lee. That .3 to .4 grain discrepancy is really bothering me. I've carefully checked zero on the Lee and RCBS scale and have installed fresh batteries in the MTM scale and the results are always the same. This is the first time that I can remember seeing a discrepancy between the Lee and MTM scales.

Considering that the Lee and MTM scales usually agree with each other -- other than for that test with the 32-20 case -- I trust them the most. The Lee scale has limitations and hassles, but I don't think it's as defective or dangerous a product as many people seem to say. If it were truly dangerous it would not still be on the market. Americans love them some legal action, so if the Lee scale was really that bad it and Lee would have been sued into oblivion by now.

The RCBS is new to me -- just a week or so -- and I have to say that I don't particularly trust it yet. I like its ease of zeroing and the ease of setting and reading each poise, but just testing it out with calibration weights has not left me with a lot of confidence.

Any suggestions for what I should be looking for or what I might be missing with the RCBS?
 
Trust the calibration weights more than any of the scales. As for the LEE scale, I don't consider it dangerous, but rather frustrating to use. However, smashing one with a sledgehammer is a great way to release feelings f frustration or stress.:p
 
I trust my two RCBS Chargemasters implicitly, I have verified them several times with bullets and test weights and they both read within .1 gn at all times with all weights tested. To me this indicates they are either both equally flawed or equally accurate, I suspect they are accurate myself.

As the old saying goes "Trust......but verify"
 
I frequently compare my Lee beam scale with my Hornady electronic powder measure scale, and they are the vast majority of the time in agreement. The only times they don't agree results in the Hornady reading 0.1 grains higher - rounding result again maybe? I just recently did up several batches of x54R test rounds and weighed each and every one on both scales just to see how it would all work out. But yes, the Lee is very very very frustrating to use when you're changing charges weights by decimals of a grain LOL.
 
Accuracy does not matter. But repeatability does.

When you develop a load, you start with the START load and then, if indicators suggest it is ok, you work up. When you decide that 44.5 is THE load for that rifle, all that matters is that you get the same amount of powder, each time you weight 44.5 with the same scales.

It does not matter that the same powder on my scales would weigh 46.3 and 42.4 on H4831's scales.

I have a dime sitting on my scales. It sits on a piece of masking tape marked 33.4 (I think that it what it says. I am not in the loading room.) When I start I weight the dime. In a long session I might weigh it again, just to make sure the scale has not gone nutz. I trust a beam scale to be repeatable. i don't trust an electronic scales, which I use all the time. That is why it has the dime.
 
Ganderite is correct...repeatability is what you want WITHIN a tolerable limit.
Invest in a small set of Ohaus scale weights, they are not expensive.
Keep the pivots and bearings in the scale clean and you will not have any problems.
An inexpensive magnetic dampened beam scale is as good as any electronic scale you will buy, but just not as fast.
 
The die sets are not perfect either. I have the RCBS one, makes for a good reference point though for other or new scales, or just cause.
 
+1 on this! I check the scale during longer session multiple times with the calibration weight and the powder pan. any electrical scale could fluctuate, more or less, due to many reasons.

Ganderite said:
Accuracy does not matter. But repeatability does.

When you develop a load, you start with the START load and then, if indicators suggest it is ok, you work up. When you decide that 44.5 is THE load for that rifle, all that matters is that you get the same amount of powder, each time you weight 44.5 with the same scales.

It does not matter that the same powder on my scales would weigh 46.3 and 42.4 on H4831's scales.

I have a dime sitting on my scales. It sits on a piece of masking tape marked 33.4 (I think that it what it says. I am not in the loading room.) When I start I weight the dime. In a long session I might weigh it again, just to make sure the scale has not gone nutz. I trust a beam scale to be repeatable. i don't trust an electronic scales, which I use all the time. That is why it has the dime.
Click to expand...
 
My main thing to watch for with scales (or any measuring device) is consistency. As long as you get the same reading time after time for the same poder load, you should be OK, as long as you don't try foolish things like maximum loads right out of the gate. If your scale is off even 2 or 3 grains, if you start at a low to mid level and work your way up, the number on the scale doesn't really matter. The critical thing is that the same load of powder gives you the same reading on the scale time after time. I have a 1 gram calibration weight and a few electronic scales, and all are within 1/10 of a grain of each other, and the Lee is very consistent, always giving me the same reading for the control weight.
 
jihmmie said:
What altitude are you at? What altitude should it start affecting different scales??
Click to expand...

That's an interesting question. I just looked it up and we're at 227 m / 745 feet.

I don't think these scales are accurate enough to be affected by barometric pressure or the gravity differences due to increased distance from the centre of the earth :)

But you might be on to something regarding environmental factors: they might be affected by temperature. My reloading room is pretty cool and it warms up from the room lighting and my body heat over the time I'm in there.

When I head into the room it's usually about 40°F (my wife keeps the house pretty cool and the basement can get chilly). After a couple of hours it can be 45°F or more. A 5+ degree change might affect the bases of both the Lee and RCBS scales or the beam of the RCBS. I don't think temperature would affect the phenolic of the Lee beam as much, but that's just a guess. And who knows what temp changes do to digital scales.

I really need to try my tests again with a warmer room and a room that's been warmer for a longer period of time.
 
For what it's worth (maybe not much).

I have 3 scales - my RCBS Chargemaster (Digital), a small Cabelas (Digital) and my very, very old Redding beam scale (oil damped! the beam has a paddle extending down into a reservoir of oil to damp the "swing" of the beam when the powder gets dumped - it's a PITA to refill when I notice it needs it, but extremely accurate).

At any rate, I have a combination of fluorescent lights, LED Strip fixtures and a goose neck lamp near the presses with a 70 watt equivalent LED bulb. When checking the digital scale weights against the beam, I sometimes noticed some serious discrepancies. But the discrepancies weren't consistent. One day there would be .5 gn to .7 gn variance, the next day all three were bang on. I was puzzled as hell as to what was causing it. I don't have anything magnetic near the bench. There are no air currents as the closest register vent between the joists in the ceiling in the basement where my reloading room is are at least 10 feet away.

Finally, by luck, figured it out. I left the fluorescents turned off at one point while reloading during the daylight hours, with the sun coming in the window. The two digital scales and the beam were within spitting distance of each other for charge weights. Turned the fluorescent lights back on and started noticing discrepancies in the digital units.

So I put more LED fixtures in the reload area and now leave the fluorescents turned off, and the consistency of the weighing is a lot better. You may find a similar problem with your lighting, or any other potential electrical or magnetic nearby interference.

FWIW.
 
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