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Old April 13, 2013, 05:35 PM   #37
Join Date: March 4, 2005
Location: Ohio
Posts: 13,648
Originally Posted by pathdoc
for example, weighing 43.0gn of my favourite target charge was sometimes a pain; I would get 42.9 or 43.1 but never the exact figure.
43.0 grs divided by 15.43236 grs/g = 2.786 g. So we can deduce that scale is a gram scale with 0.01 g resolution converting grams to grains, and as it jumped back and forth between 2.78 g and 2.79 g internally, you got 42.9 grs and 43.1 grs after rounding.


Per Bumblebug, it sounds like a powder measure might be better to increase your production rate. The only problem is the kind he suggested and others like it cost several times more than the scales you've been considering. I'd recommend you look at the Lee Perfect measure, which is $22 at MidSouth, and you can calibrate its settings with your 5-0-5. That measure does well with stick powders and large grain spherical propellants, but has issues with fine spherical propellants getting wedged between the rotor and drum. It can be made to work with them, but a bit of effort is involved.

Also note that no measure can be totally counted on to do better than about 0.2 grains precision with stick powders, but fortunately they seldom need to. Stick powders tend to be more forgiving of exact charge when dispensed by volume as packing tighter slows their burn rate a little and vice versa. You can read Dan Newberry's pages on developing a load with best immunity to charge variation without changing point of impact.
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Last edited by Unclenick; April 13, 2013 at 09:22 PM.
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