Yesterday, .45 Schofield. Someone on another board sold me new brass to use with a SAA. Loaded at 4.2 gr Bullseye and a 250 g lead FN coated bullet. This resulted from a robust discussion whether a lighter BE load in a big .45 case could explode...lighter was 5.5 gr BE.
There has been speculation for years that small amounts of fast powder will detonate in larger cases in a certain circumstance. That circumstance was that the powder didn't immediately light off and the primer blew the powder forward in the case before it lit off.
Since I was a boy, we used small amounts of Bullseye in just about anything we shot. It was developed by someone in the family so the kids could shoot 30-30's, 1903's etc. without any recoil.
It appears they were right as some years later, Ed Harris and some other folks at Fairfax Rod and Gun and the Los Angeles Silhouette Club were doing the same thing.
I never experienced a blow up with a small amount of Bullseye in a large case. Now, a double charge of Bullseye, well, that is a horse of a different color.