|
I played around with the "scoop through the powder" and "sink the scoop in the powder" methods tonight. In the interests of speed and ease of reading scales, I used my little Frankford Arsenal digital scale, which is accurate to 0.2 of a grain. I figure this is fine if I'm well away from maximum (which I am; 42 grains for the 174gn bullet; 43gn for the 150gn bullet). I used the 2.8cc scoop that came with my .303 Lee Loader kit, and the expected weight as per the enclosed powder chart was 38.3 grains of Varget.
Pouring some Varget into a bowl to an adequate depth, I scooped 20 scoops using each method. Although this is fairly low, it was dictated by time constraints and the assumption that the shooter with a Lee Loader is going to do no more in one session than sit down with a box of fired cartridges and reload them, so a larger sample size may not be relevant. I zeroed, turned off and recalibrated the scale after each lot of 20. I struck the top flat with a card before dumping each scoop in the pan.
I plugged the numbers into Microsoft Excel (raw data below; apologies for the post length), and got the following number crunches:
"Scoop through the powder" method (weights in grains, of course):
38.4
38.4
38.7
39.4
38.7
38.7
38.0
38.4
39.2
38.4
38.9
38.3
38.9
37.3
38.6
39.2
37.8
38.4
37.8
37.5
Average 38.5gn, St. Dev 0.6, Max 39.4 Min 37.3, Spread 2.1gn.
"Immerse the scoop" method:
38.7
37.3
38.4
37.8
36.9
37.5
38.0
37.3
37.0
38.0
37.8
37.5
38.0
37.3
36.6
37.5
38.6
38.3
38.4
38.4
Average 37.8gn, St Dev. 0.6; Max charge 38.7; Min charge 36.6; spread 2.1
I'm pretty sure I've applied the formulae correctly, but the raw data are there in case anyone thinks my standard deviations and spread of min and max charges are suspiciously identical and wants to recheck them in a stats program (I was certainly surprised!!!).
All this (with a strong caveat for the small sample size) suggests that the scoop-through method provides a charge closer to stated weight, but that there isn't much variation of accuracy between methods.
|