I can understand the theory.
The balls can also obturate when fired.
Here's some balls that were fired from an ASM Colt Sheriff that was stored loaded and lubed for a long time that resulted in weak powder and which were basically like weak squib loads.
I recovered them after being fired through a paper target into foam target backing.
The portion of the balls that contacted the rifling seems to be fairly substantial.
I don't recall if this ASM's chambers were swagged or not.
Can you tell if the balls were cut or swagged when loaded?
I didn't load it but from the deep ramming rings on top of the balls they look like they were slightly over-sized.
Perhaps every gun or brand has slightly different barrel and chamber dimensions.
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I guess you’d need to check the diameters and compare it to the groove depth to see if they filled the bore or not, assuming the chambers are undersized.