It's been said many times, but here goes again; The brass is stretched where the bulge is, you run it thru a Bulge Buster to make it fit back in the chamber, BUT, it does nothing about the fact the metal was overstressed in that spot. Reload it, shoot it again, and the previously bulged spot loads in a supported position - the shooter thinks they solved a problem. They didn't. They just got lucky. Repeat until the bulge happens to load in the exact same, unsupported position and get a Kaboom!. Then spent lots of time and effort trying to "figure out" what happened.
Lather, rinse, repeat endlessly
IMHO Bulge Busters are 2-purpose tools;1) Make the case fit back into the chamber, 2) Give the reloader a false sense of security. The 'plunk test' only reinforces the trick. It tells you absolutely nothing about the condition of the case except it will fit.
Ask yourself this question; If you had some bottleneck cases with the prominent ring around the head indicating an imminent head separation, would you run it thru a 'bottleneck bulge buster' (if there was such a thing) and shoot it? ? ?