Your gun blowing up may have had nothing to do with winchester or BPI, your trip 7 may not have actually been trip 7.
===============================================
Hodgdon has been known to occassionally leave an overhead feeding tube of Pyrodex behind for the first few jugs of 777 at the filling station of their plant, but to the best of my knowledge, no cartridge smokeless powder is bottled or kept at that facility.
Last year, I smelled sulfur while shooting my 777. I returned the 1/2-used jug that I estimated was at least one-third filled with Pyrodex Select by HAZMAT-regulated method & was rewarded with a very generous supply of 777 powder a week later.
Great folks at Hodgon Inc.