19th century British powder grade?

[Kno-ie]

Looking at Research Press's writings of the Whitworth rifle I've noted a statement of " 6 size powder of the best quality ".
What is the modern size equivalent.
Thanks
Kno-ie

 

[ResearchPress]

Looking at Research Press's writings of the Whitworth rifle I've noted a statement of " 6 size powder of the best quality ".
What is the modern size equivalent.

Curtis’s & Harvey sporting gun powders were numbered, the higher the number, the coarser the grain. Insofar as I can ascertain, Swiss No. 4 (1.5Fg) would be a similar size to C&H No. 6.

David

 

[Kno-ie]

David,
Thank you sir.
Kno-ie