Richard Lee's 2nd Edition of Modern Reloading (2003) has a short section in Chapter 2, page 52, regarding possible excessive pressure caused from reduced charges of slow powders. The basics:
1) very slow powders with small caliber large capacity cases,
2) reduced charges by 25-35%
3) something bad happens that no one appears to be able to conclusively explain
The theories for 3):
1) wave pulses
2) bullet starts then stops, excessive pressure builds before it moves again
3) powder compresses against the shoulder, forming an obstruction
4) a small charge evenly distributed horizontally acts as a shaped charge and directs pressure to a small area on the top of the chamber
The Lee book uses reloading data from the powder companies.