Many of the earlier brass shotshells used primers which were not hot enough to sufficiently light powders other than Black, Bulk Smokeless Shotshell, or the fast smokeless powders such as Red Dot etc. If using cases taking large pistol primers the use of magnum primers should expand the use of some slower powders. Those taking the regular 209 shotshell size primers should properly ignite most any smokeless as long as proper wads are used with a snug fit to the case & the top wad securely sealed.
My first experience with brass shells was with the old Fiocchi hulls imported by Alcan Inc & using 645B Berdan primers. I loaded these with a smokeless flake powder called Nike which gave good results, but they would not properly ignite slower powders for a heavier load. The only downside I ever found to this was the chore of decapping those pesky Berdan primers.
