So, grading powder...
There's a tolerance for commercial powder. 3% can get away with
not passing the first, coarse screen, and it's ok if 12%
does pass through the finer screen. That's the tolerance, or at least how I've read it stated in many references.
When I grade my powder, there is
no granted tolerance. If it does
not pass through a given screen, it's pulled off and sorted as a different grade or re-processed. Same with the finer, "hold" screen. It either holds, or it doesn't. If it goes through the finer, hold screen, it is sorted as a different granulation, or re-processed. I'm guessing it's much the same for you guys.
With my fffg, it's even more stringent, due to the way I do it. Grade fffg is, according to everything I've read; 3% pass 20, 12% hold 50 mesh. So theoretically at least, ya toss your powder on a 20 mesh screen with a 50 mesh screen below it. Whatever passes through the 20 mesh screen, but "stays on" the 50 mesh screen, is bona fide "FFFG" powder.
However, when doing mine, I don't do it quite that way. What I do, is catch what my 30 mesh screen doesn't stop when doing ffg, and try it on a 50 mesh screen. What stays on the 50 screen, I call fffg. So my personal fffg powder, is actually 30--> 50 mesh powder instead of 20--> 50, and with zero tolerance besides that!
So, my powder is just that much more consistent and better than factory, commercial powder, right??
;~)
Vettepilot