Please don't be offended by my questions and forgive my wordiness... What type of scale are you using? Do you weigh each load? Have you moved anything that would--or could--change the atmospherics around your loading area? Same for powder storage area? Change electronic layout in any way within five feet of your scales? Ferrous metal storage change?
This long-winded and there's several influential factors at work here left undeclared for brevity, but the reader will no doubt pick them up. A short time ago I had my Sartorious begin acting up. I checked the balance's calibration; it would verify and then continue to travel up and down, sometimes as much as two grains, with the 1000 grain weight on. This happened in late August. It starts getting dark at night in late August and my Toyo kicks in some nights. It was a "dark" fall, and wet, this year so the Toyo ran more frequently than normal. I was also making up loads later and in greater number than normal as well. I keep the temp 51F after the butchering is done until around May first. Then I move the thermostat to 60F because I'm sitting (not skinning, butchering, or other shop work). It was set at 60F. I set three milk crates one atop the other and have a board fitted to act as a table top. This year I misplaced it so just put a couple short sticks and a sheet--galvanized--metal over them making my storage excess table up again. Alas, when the the Toyo began running it drafted the scale (just a short glass shield on this one) differently than ever before. I moved the table/stand farther away after trying other things. It reduced the span of change, but didn't eliminate it. Then one night I came across my fitted top and put it back, removing the galvanized sheet and sticks. The span diminished more, but still didn't go away returning to normal. However, I just set the galvanized sheet aside--still within four feet of the scale. Only when I used the sheet for another purpose did the scale return to normal. I found that moving ferrous metals within five feet of the scale could effect it. That bugged me so I started experimenting. You know those little cylinders on wall chargers and some computer electronics? They're magnets. They definitely influence electronic scales. I found when I put one three inches from the service line's entry into the scale it "calmed" the scale considerably and when I put a "genuine seal" magnetic money clip about a foot from the wall outlet on the same line the scale worked the best--and most accurately--I ever experienced.
I'll spare you an experience I had a few years ago with a powder that was considerably more hydroscopic than others I've used. suffice it to say high humidity, maybe coupled with high atmospheric pressure, added weight to this powder. I lost over 40 fps with these loads. Happy it didn't go the other way.
