Lee Loader

Very educational: https://www.vihtavuori.com/tech-blog-po ... in-shapes/

I'm trying to picture the "die" that forms the multi-hole perfs.

Make smoke,

The perforated powders must be fast burning.

Actually ........
The powder for the 5"/38 , 8"/50 and 155mm Howie have 9 holes and the kernels are big enough to readily see the light though .
Think 150+ lb bullet on 50-55 lb of powder in a 400" barrel 2750 fps on 34,500 to 35,200 psi at the breach .

Coatings and the perferations do control burn rates but also curves . It's all about surface area ........