Accuracy of balance scales

EccentricInTexas said:

I switched to a digital scale I think it was about 35$ from Academy. I noticed the same thing with my beam scales. I think unless you are matching every bullet neck diameter and case I doubt you would notice the difference unless the scale is seriously wrong. The digital ones take up a lot less room. One thing I strongly suggest is getting either a brick or a slab of polished marble to set the scale on to zero it that way you know it will not get bumped slightly and change.

Click to expand...

And let it warm up and keep it away from fluorescent lighting

I'd like to know what a charge *really* weighs, and to know that a 4.0 grain charge I weighed today is the same as a 4.0 grain charge I weighed a month ago....What would you do?

Click to expand...

Get standards in the range of weights you are wanting to weigh and keep them handy.

Bill M. said:

..... a set of check weights.....

Click to expand...

For a two poise 505grain scale only two weights are needed. One 450 grain, one 4.5 grain. That will allow you to check the poises. Everything else is a rabbit hole.

Gravity will never let you down. Just don't bang your scale around and keep the 'movement' clean.

Check weights are really overkill if you have an OHaus scale.

You really only need a reference or two. Weigh a dime and weigh a silver dollar. Write the weight down on each of them with a Sharpie.

Those two references tell you that you are measuring the same today as you were the last time you weighed.

Think about it...you are really trying to match the load that you weighed last time. It does not matter if that load was really 44.908 grains or 45.104 grains. If your scale showed 45 then and shows 45 now, you're good to go.

Very unlikely a scale is "off" at the low end. The only errant part is the poise whose "error" shows up, or is "multiplied" at the high end of its travel.

A CLEAN scale is a happy scale.
RE-ZERO for level.
NO AIR MOVEMENT please!

Sigh........... if only I could hold a pistol on target well enough to know the difference tween +-1/10 of a grain.

a__l__a__n said:

To illustrate why this matters to me: I'm loading 3.2 grains of HP-38 with a 90 grain XTP for 380 auto. I want velocities from my LCP II to be in the 800 to 850 fps range, which seems to give the best performance based on the youtube gel tests (FWIW). So if that's my design goal, I can tolerate +/- 0.1 grain but not +/- 0.2 grain. If I calibrate my powder dropper for 3.2 grains, I am confident it won't drift more than 0.1 grain, plus or minus. But if I think I've calibrated it for 3.2 but the scales were off by 0.1, it could really be calibrated at 3.3 grains, and the drift could take it to 3.4, and the velocity goes outside my parameters. (or similarly for variations on the low end). That's assuming my OAL doesn't vary. If I get a slight setback it could add even more velocity, taking it outside my design parameters. So each source of variation is independent of the others, and if they all vary together the resulting error escalates. To get consistent performance I need to control each source of variation.

Click to expand...

I understand where you are coming from entirely. Way back, when I was competing in UIT precision pistol matches I was using .32 semi-auto pistols, Walther, Pardini, Hammerli and the like. These pistols used a .32S&W Long full wadcutter cartridge, the load for a 98gn bullet was 1.5 gn of Bullseye. As these were straight blowback pistols, with a fine line between maximum accuracy, minimum recoil and 100% reliability, weighing the powder to fine limits was a necessity.

An inexpensive digital balance is the way to go these days in our electronic age. Beam scales are still extremely accurate and will last many years if kept clean and maintained well. Most if not all industrial and college laboratories have switched over to the single pan electronic balance and have made an antique or those beam scales. Matter of fact I have a wood and glass antique two pan scale that I refurbished sitting in a place of honor in my rec room and have two electronic digital balances in my reloading room.

If I calibrate my powder dropper for 3.2 grains, I am confident it won't drift more than 0.1 grain, plus or minus. But if I think I've calibrated it for 3.2 but the scales were off by 0.1, it could really be calibrated at 3.3 grains, and the drift could take it to 3.4, and the velocity goes outside my parameters. (or similarly for variations on the low end). That's assuming my OAL doesn't vary. If I get a slight setback it could add even more velocity

Click to expand...

Any bullet setback is going to be a deal breaker with such tiny case volume.

One of Speer’s tests showed pressures more than double with a .030” difference in seating depth, in a larger 9mm case. Only going to get worse in a smaller case.



I have one Dillon powder bar that the last time it was adjusted was 2003 or 2004, it throws the same charge, to the tenth, every time I check it and amazingly even with many different lots of powders over the years.

However, you are not talking about accuracy or your measure but the ability of your scale to indicate an identical weight over time.

For this you just need a “standard”. It doesn’t have to be anything expensive or very fancy, all it needs to be is something that won’t change its mass over time and weigh close to what you are wanting to weigh.

For example, if you took a spent large primer, knocked the anvil out of it, cleaned out the residue and weighted it, you’ll be close to your target. Sand it a bit and you could get it right on your 3.2 grain target. Whatever it weighs when you are done is what it will weigh next month, next year, 5 years from now.



Now get a container you can’t lose, label it with the weight of the object you are going to keep inside it and keep it handy. If your scale says the object weighs different one time than it does others, I would trust the object didn’t change and your instrument is not telling you the truth.

I had a digital, and for some reason it would "wander" after a few minutes, so I was constantly rezeroing with the included check weight. I eventually gave it away to a local pawn shop. No, I didn't pawn it - I literally gave it to them.

Digital scales vary a lot. I have the FX120i as shown in a previous post. On a good day, my cheap Gem Pro 250 in a very stable environment, after a lengthy warm up and under the right lighting, JUST MIGHT read as well, but no where near as consistent.

Bob

a spec of grime on the smaller beam weight for grain fractions, will throw off lower weighings from what I've found. I checked against a digital scale, and eventually the fix was to remove weight/decades of accumulated grime, from the smaller weight. I think the behavior was it was weighing light 1/10 ish grain. Once cleaned, it measured correctly to less that 1/10 grain. I was playing with like 2.2 grain .32 ACP loads and 1/10 grain variation wasn't good enough IMHO.

Fluorescent lights and/or their electrical components have a tendency to affect the electronics on digital balances and cause them to wander. The higher quality laboratory balances are shielded against this electrical interference. However, the balances we buy and use for reloading are not. Worked in the scientific field for 38 years, so I speak from experience.

However, the balance doesn't settle consistently. Sometimes it returns to level and sometimes it is off by a half of a tick mark, sometimes more than that. Tapping it again might return it to level.

Click to expand...

That would make me look for signs of contact between the beam and base. Assuming the two points of contact are proper and clean, I would make sure the beam is not in contact with either of the sheet metal stops.

Like this


Or this


But centered between the two.



While in that position make sure the pivot is square with the beam and the damper and pointer is not making contact on the other end either.



If everything checks out good but it still is erratic, I’d look up Scott Parker and send it to him. He is pretty well known for getting them to work better than new.

Let’s make sure your Agates are clean and free, another place to inspect is the main poise washer to ensure there is not a burr or damage preventing the washer from centering on the V groove

Some great info in this thread!! My 10-10 started acted erratically years ago and I don't hardly use it any more. I have a chargemaster lite that I use when I weigh charges now, and a Gempro 250 that I use to verify stuff. But I agree that electronic scales are sometimes a little wonky. I might dig out my 10-10 and look at some of the fixes suggested. Thanks @spj and @jmorris

Laphroaig said:

My 10-10 started acted erratically years ago and I don't hardly use it any more. I have a chargemaster lite that I use when I weigh charges now...

Click to expand...

Might play with your CM a little and see what it’s not showing you.

View attachment 960028 View attachment 960029

Just a little thing to keep in mind is that these old scales are collectable, especially if you have items that are essentially mint and with the original box. I have a small collection including an old Herter's that is pre-magnetic damping. It is oil damped and has a reservoir for whatever viscosity of oil you feel is appropriate. As mentioned before in the thread, accuracy of most beam scales is +/- 0.1 grain. You can actually adjust the calibration on some of them. They are generally calibrated with lead shot and there is access on some scales. The M5 scale on the left has a screw/nut on the platform the pan sits on. The lead shot is in there. It really isn't recommended that you monkey around with it though.

As far as digital scales are concerned, the are picky little sensitive beasts. I keep a digital thermometer/humidity gauge on my bench. I warm up my scale or measure (I have one of each) for at least an hour before I do a calibration. Once I am calibrated and set, I pay attention to the thermometer. If the temp changes up or down more than a degree, I stop an recalibrate my scales. I would do the same for a largish change in humidity, but I do live in a desert, so I don't have a lot of shift in that department.

Also, a thing to look for is a ferrite core on the power wire to the scale/measure to suppress the noise being transmitted through the power wire. My Chargemaster Lite came with a core, but my Rangemaster 750 did not. I purchased a core and installed it on the power wire.