[Fairshake]

All BP burns from the outside in and unlike smokeless powder it's all the same. By that I mean that in the making of BP, the three chemicals are mixed together with water and it's compressed into a large look like hockey puck.
Some powder makers use what is called a ball mill to break it down into the needed grain size. Goex uses the wheel mill.
Your Fg powder and 3 F powder are the same with the only difference being the grain size and how long it's refined.
If a company leaves it various grain sizes in one batch then that powder will burn slower than one that has all of the grains about the same size and smooth outer surface. This will make for a faster burn.
Take a slide of 3 f and 2f and look at them under a microscope. You will understand right away why the 3f produces higher velocity.
Look at Swiss powder and then Goex and you will see why the Swiss is a better and more consistent powder.
In BPCR shooting you will have some bullets that are seated on a compressed charge of .385 and above. These rounds are very accurate.
The top shooters are even placing newspaper or tissue across the primer flash hole to even out the flash and receive a better burn for it.