Straight ball powder is very regressive burning. Virtually all ball powders whether shotgun, pistol or rifle are thus coated with a deterrent to slow down their initial burn rate & make them more progressive. This also makes it harder to ignite.

For shotshell reloading, I have almost universally used Hercules/Alliant powders.

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