For years I did not know what the difference in Infallible & Unique was. Some statements seemed to indicate they were identical. If so, Why did they sell both? Early loading data listed only Infallible for shotguns with Unique for pistols & light rifle loads. Infallible was eventually dropped & Unique began to be recommended for shotshells as well.
Finally, I found out the difference. Both powders had the exact same chemical composition & both were a flake type powder having the same diameter of round flakes. Infallible flakes were .3mm (.012") thick while Unique flakes were .35mm (.014") thick, thus Infallible was just a wee bit faster & also a bit easier to ignite with early shotshell primers.
I found this in an old American Rifleman article on shotshell propellants.
