I think they changed some of the potassium nitrate against potassium perchlorate to elevate ignition temperatures and reduce sensitivity of the bp.

A way to adapt it to the modern human perhaps? Daryl is right, use ordinary bp, the perchlorate gives chlorate gases when burning, and those gases eventually turn into hydroclorid acid.
If you go and have a hamburger after a session at the range, and not right home to clean the rifle, it will corrode at some time.