Big Al;
From an old NRA Handloaders Guide; Screen opening for duPont sporting BP;
Screen Opening (square mesh)
Powder
designation--Pass----Hold
Whaling ----.4410"--.1560"
Life Saving-.1310"--.0650"
FG ---------.0689"--.0582"
FFG --------.0582"--.0376"
FFFG -------.0376"--.0170"
FFFFG -----.0170"--.0111"
Note that not all companies used the same standards.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra