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In the late 1800s the British created dum-dum bullets by cutting the solid lead bullets of a cartridge. There would be no reason to do in in modern times with hollow points and other defensive ammo available. Obviously, the purpose was to create a larger wound cavity than a bullet that remained whole and passed through the target.
There was a Dum Dum arsenal near Calcutta in India where the British are said to have done this. Not the most effective way to make an expanding bullet but if all you had were solid lead bullets you might do it.
It was probably more useful in cutting some of the full metal jacket off the tip of jacketed bullets when they were introduced. I am always amazed how "pointy" the full metal .303 British bullet are that are used in my Enfield rifles...

EDIT: Who you calling old whippersnapper!!!????