Hello, all!
Rifle Bore Cleaner was manufactured to a Mil-Spec that dictated product performance, and not a specific formulation.
The WWII Rifle Bore Cleaner is very different from that used since the late 1950's through the Vietname War era.
YES, the WWII stuff can, and did, separate into it's component parts and was famous for stinking to high heaven! It was also mildly toxic if inhaled for extended periods.
The recent production Hoppe's Number 9 solvent (since the early 1990's) is not as potent nor to the classic formulation as the Old Hoppes #9. The word is that the old formulation contained hazardouz materials (bezene, a known carcinogen) and left the Manufacturer open to liability issues.
On another board, a poster wrote that one of the Canadian Government Laboratories in Edmonton, Alberta, I believe analysed the infamous Red's Bore Cleaner and found it be nothing more than aircraft diesel fuel and ammonia with traces of other hydrocarbons.