So I weighed most of a tin of pellets, but there's story here.I was looking for something to do with a 15 year old mentee that was coming to visit yesterday and decided something involving manual lab skills, measurements, precision, and statistics would be nice...ah, weighing pellets! I've been wanting to do a tin anyway. The original plan was to use a mechanical balance, but that would have been slow going. (Still a good exercise though!) However, I happened to be in another shop and they had a nice electronic analytical balance that could resolve to the nearest milligram. I asked to borrow it and took it to the shop. At the last minute the kid had to cancel, but I decided I should at least preview the assignment to make sure I wasn't asking him to do stupid work. (I hate assignments like that...)Long story short, these digital scales are nice, but you do have to work in a draft free space if you want it to settle on a number to the nearest milligram. In retrospect, I could have set the scale to grains, but then again, 0.01 grain is smaller than a milligram and a little more work to wait for...Anyway, I pick a pellet that is close enough to 8.4 grains and make that my "standard"--always and frequently zeroing the scale with that pellet, keeping it separate from the others. That way every pellet is +/- some small number of milligrams from that and I only have to write bin labels like 0, +1, +2, -1, etc. By the way, another thing about these scales is you should plan to verify the warm up time needed. I found that for the first few minutes the zero kept creeping away on me by a milligram or so. Once warmed up, it wasn't a problem. (Now, if I had a 20 gram range scale in the first place, there might be less warm up, but this unit was 210 gram capacity...)After some time, I managed to weigh the whole tin (and reweigh some of that, as the case was...). I'm pretty handy with tweezers and developed a routine: after putting one on the scale, I'd pick up the next one; by the time I had it ready to put on the scale, I'd read the weight of the one on the scale, set the next one beside it and snatch the weighed one, binning it and picking up the next pellet while the scale settles on a number.Looking at the little petri dishes with the pellets in them, it didn't look like a nice Gaussian distribution (bell curve), but I used the scale to count them--an awesomely handy feature!--and plotted the data...Viola! a bell curve! (Below) I was half expecting there to be multiple concentrations, e.g. output from several distinct dies, but instead it does appear to be a normal, er, rather a typical (shouldn't use "normal" here--that is another type of statistical distribution...) bell curve type group. Good to know, for what it's worth. I'm curious next to see if the 550 mg pellets are much different than, say, the 545 mg pellets. The whole range of the chart amounts to +/-1.6 percent variation about an average of 546 mg (8.38 grains), so that seems pretty tight already. In grains, the data runs from 8.29 to 8.56 grains. Enjoy! Please chime in if you've seen trends for other pellets. The only thing I'll add here is a musing about the inexpensive digital gem scales you can get on eBay and elsewhere these days...A 20 gram range is going to help you (as opposed to 200 gram), but are they good? Once this unit I had access to was warmed up, everything was repeatable to the milligram. I saw a guy test a cheap gem scale on Youtube and he got three different numbers for the same pellet...Anybody have any experience to share regarding those?
run that test again at 40, 45, 55 yards and see what ya get.......
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