Powder scale accuracy observation

[croue]

OK,
I was weighing and dumping and refilling cartridges like crazy to get what my scale said was an accurate powder load.

But I found something that seems really odd.
I have a small Hornady electronic scale. I would tare out with the brass case, drop the powder and then weigh the powder charge. Works pretty simple. But many times the charge would vary up to 10% or more - definitely not acceptable. This was driving me nuts, adjusting the rotor, chasing the charge weight around.

Then I started using the aluminum pan that came with the scale and just did some experiments. Single drops went to +/- less than 0.1 grains on a 4.7 grain charge more than 90% of the time. Occasionally measured out by 0.2 grains. Like once in a 200 round lot, measuring a single charge every 10 rounds, and a 10-charge drop at the same time for average. The average was always within less than 1 grain for the 47 grain target. Most of the time within .2 grains.

So what's going on? I have far more confidence in my powder drop now. But why doesn't this work when I use the brass case as my 'pan'? The results are NOT the same. But I can dump the powder from the brass into the aluminum pan and the charge is right on.

Anyone else have this issue? I like dumping right into the brass, no funnel. And I am confident that my drops are quite consistent (although i still do my 1 and 10 charge check every 10 rounds).

C

[bubbala]

if i'm reading you right you're using a different case each time you throw a charge?
cases will vary in weight that's why bench rest shooters will weigh and group cases. it will reflect on pressures and other factors.
what i'm saying is it's the case that varies in weight not the powder.

[JMP]

What type of powder drop do you have (how do you get it into the case)? It could be on the transfer from the drop to the case. If you tare the sized and primed case it should work.

That scale is not great. Make sure the case has settled when you tare and it remains at 0.0gr after taring. Then test the calibration with a known weight, it should come with a weight 50g or 100g weight. When you tare so frequently, the calibration of the scale may drift. With the pan, you don't need to tare each time since it's the same weight. The electronic scales need to be recalibrated from time to time.

Also, if you are working outside or if their is an ambient draft, it will change the results in such fine measurements. That's why many scales have a transparent housing around it so it isn't influenced by a draft.

[JMP]

if i'm reading you right you're using a different case each time you throw a charge?
cases will vary in weight that's why bench rest shooters will weigh and group cases. it will reflect on pressures and other factors.
what i'm saying is it's the case that varies in weight not the powder.

I took it to say he is taring with each different case, so that wouldn't be the issue, but taring each time may throw off the calibration.

[croue]

I do tare each case and still get odd readings.
fer'instance. I'll tare a sized and primed 45 case, drop the powder (WST in this case) from my Hornady powder drop with the pistol rotor. Aiming for 4.7 grains. Weigh it, and it may read say 5.0 grains.
I'll stop, tare the aluminum pan, dump the powder from the shell, and tap every bit out and get 4.7 grains on the nose every freaking time.
It's like there's something wrong with putting a brass case on the scale. Can't be can it?
I'll recheck the tare on the empty case several times, and it comes up good. Driving me crazy! But last nights experiment and 200 round run with good results using the aluminum pan as the 'check' went great. Maybe I do need a better scale than the little cheapie that came with the press in their starter kit?

[rdfact]

Perhaps the scale is more consistent when using the pan because the weight is spread out over a wider surface area?

[blockfort]

How long do you let the brass sit on the scale before you hit TARE?
How long do you let it sit after to make sure there is no drift?
How long do you let the filled case sit on the scale?
How long have you left the scale on to see if it drifts naturally?
Is there a fan on or are you breathing near the scale?
If it is plugged in, is the cord near any other cords?
Have you tried putting the same weight on different parts of the scale to see if it varies by location?

[Spyguy]

What is the tare weight of an average case?
What is the tare weight of your powder pan?

Sometimes an electronic scale needs more of a pre-load in order to weigh accurately.

[bubbala]

well it's an odd way to throw powder.
get a funnel.

[Whatisthis?]

Perhaps the scale is more consistent when using the pan because the weight is spread out over a wider surface area?

This is probably it.

I have a cheapo electronic scale that came with the pan for weighing charges. When I dump my powder onto the pan, if it's not spread out correctly, the weight can vary +/- .2 grains. IDK if this is completely normal or not, but I've verified weights before and it's right on if I do it right.

[Whiterabbit]

Have you observed what happens when you move the case around on the stage of the scale?

[croue]

Have not tried different positions.
I will do that.
The 'spread out' theory sounds not totally crazy.
I'll play around a bit more and get back with results.

[croue]

well it's an odd way to throw powder.
get a funnel.

I have funnels. But generally I like to drop the powder directly into the case from the Lock-n-Load powder drop through the little adaptors. Much quicker and simpler than using a funnel. I don't like the static buildup on the funnel either. Powder doesn't always flow nicely down the sides.

I am only using the pan to keep checking my charge consistency. When i start loading hunting rounds for my 270 I will go to using the pan to meter out the charge and funnel it in. But for general 'range rounds' that seems like the juice isn't worth the squeeze when you're loading lots of rounds. More suitable for small lots that I want to be perfect. That's maybe 50 rounds a year though for final sight checks and the actual hunts.

C

[Wrangler John]

Electrons are quantum entities, subject to uncertainty and probability. Even the electrical energy of your body and nervous system can influence the scale if it is sensitive enough, especially if the blanking function is set too low. (That is why computer builders wear a wrist ground strap to prevent electrostatic discharge when handling bare chips to avoid burning out delicate circuits.) Brass is copper and tin alloy, placed on a dissimilar metal plate it can cause a galvanic transfer of electricity. If the sample pan that came with your scale is aluminum, and was anodized or has oxidized, it is non-conductive as aluminum oxide is an insulator. Every source of static, radio frequency energy, and electrical noise, including the circuitry of the scale itself, will influence the reading. You are not reading the actual weight, but the conductivity of a strain gauge, which is suggestive of the actual weight based on a calibration standard. How the plate is suspended and connected to the measurement cell(s) also effects the measurement mechanically. The cheaper the scale, the more pronounced the error.

Gravity in a given location is a constant, while temperature and air currents may influence readings, a balance beam scale will remain accurate indefinitely and is not subject to interference when maintained properly.

I do not use inexpensive imported electronic scales for handloading.

[rdfact]

I have funnels. But generally I like to drop the powder directly into the case from the Lock-n-Load powder drop through the little adaptors. Much quicker and simpler than using a funnel. I don't like the static buildup on the funnel either. Powder doesn't always flow nicely down the sides.

I am only using the pan to keep checking my charge consistency. When i start loading hunting rounds for my 270 I will go to using the pan to meter out the charge and funnel it in. But for general 'range rounds' that seems like the juice isn't worth the squeeze when you're loading lots of rounds. More suitable for small lots that I want to be perfect. That's maybe 50 rounds a year though for final sight checks and the actual hunts.

C

Get some powdered graphite (aka graphite lubrication) and coat your funnels, powder measure, etc. Auto parts stores usually carry it.