"As long as both bullets are touching, from the experiments in Hatcher's Notebook, likely both bullets would be discharged without damage. There would be excess pressure on the cartridge case."
I disagree!
What you are essentially saying is that the powder load for a 9mm with a 90 grain bullet is the same as the powder load for a 9mm with a 180 grain bullet (if you can find any)?
With a 90 grain bullet:
N-330 From 4.6 grains to 6.5 grains
CCI-500 Primer
N-340 From 4.7 grains to 6.8 grains
CCI-500 Primer
N-350 From 5.4 grains to 7.8 grains
CCI-500 Primer
With a 150 grain bullet:
N-330 From 3.5 grains to 3.8 grains
CCI-500 Primer
N-340 From 3.9 grains to 4.2 grains
CCI-500 Primer
N-350 From 4.4 grains to 4.7 grains
CCI-500 Primer
With that 180 bullet load:
N-330 at 6.5 grains pressure would be in the area of 107002 PSI
N-340 at 6.8 grains pressure would be in the area of 106264 PSI
N-350 at 7.8 grains pressure would be in the area of 117025 PSI
In a semi-auto you will be picking pieces of the gun out of your body, in a revolver, with a large cylinder gap, you might get away lucky with just a ruined firearm.