We're always talking about the loads we use. One guy says "I'm using 100 grains of T7 under this bullet" and another guy says "I'm using 90 grains with that same bullet". So, are they actually using charges that are ten grains apart? Maybe. Maybe not. It's quite possible they are using almost exactly the same load. It's equally possible their loads are 15 or 20 grains apart.
It has always been my understanding that volumetric powder measures are calibrated based on FFg black powder. Therefor, all measures - when set on 100 grains and filled with FFg black powder - should throw a charge that weighs "pretty close" to 100 grains, right? Of course, forum regulars realize that 100 grains volume of Pyrodex or Triple Seven will weigh less because those powders are not as dense as black powder.
Anyway, I was preparing my gear for the upcoming experiment with weighed balls in the Great Plains flinter and decided to eliminate as many variables as possible by also using weighed powder charges. I've posted many times that this gun favors 95 grains of GOEX FFFg. I planned to fill a few dozen of Lane's powder tubes with that load. After setting up the scale for 95 grains, I filled my TC U-View powder measure to the 95 grain volume mark and dumped it in the scale's powder pan. That charge did not even move the scale's balance beam. After making adjustments I found the 95 grain volume charge actually weighed 84.3 grains. At about this time I recalled that Cayugad once commented that the velocities I posted for my 95 grain load seemed low. Sure enough - it's really an 85 grain load. So I proceeded to load my powder tubes with 85 grains weight.
After filling the tubes I began to play around.
I filled the U-View to the 100 grain mark with GOEX FFg. That charge weighed 91.5 grains.
I filled the U-View to the 100 grain mark with GOEX FFFg. That charge weighed 89.5 grains.
So clearly, the U-View is throwing "light" charges. Now I'm curious. So I get out my twenty year old H&A brass powder measure.
I filled the brass measure to the 100 grain mark with FFg. That charge weighed 95.4 grains.
I filled the brass measure to the 100 grain mark with FFFg. That charge weighed 94.0 grains.
BACK TO THE BEGINNING: Now add in the differences in how people fill their measures - tapping/not tapping, pouring quick/pouring slow, etc., and it's easily possible that guy #1's powder measure set on 100 grains is actually throwing 105 grains, and guy #2's measure set on 90 grains is really throwing 80 grains - a 25 grain difference. It's just as possible that both measures are throwing 95 grains.
