For those interested.
The brinel hardness of quenched lead, bullets or balls will depend on the temperature the lead is as it hits the water. Temperature used in casting has
a great deal to do with this.
WW alloys, the old stuff around 10 to 13 brinel, due to the 2 or 3% arsnic in it, will heat treat as the chart notes to considerably harder alloy. Balls or bullets cast from lead shot will do the
same, due to the arsnic in their composition. IIRC 1% is about all that is needed.
Pure lead and tin alloys, nor straight PB(lead) and antimony mixes will water harden.
We also put cast bullets of (the old) WW in the oven (when wife is not at home) and cook them for 1 hour at a temperature that is just below slumping, then remove and dump them into a bucket of
water, with a folded towel at the bottom. The balls or bullets will still be soft, so at this time, immediately lubricate them. Over the course of 11 to 12 hours they will harden as they sit at room temperature, to upwards of 30 to 34 brinel. If they are sized and lubed after they are hard, the surfaces "worked" will soften- thus, sizing and lubing immediately after quenching is necessary.
Cast bullets or balls hardened this way, can be made harder than any other method of mixture of lead, tin or antimony. Dead soft copper has a brinel of 34/35.
I have been 'doing this' hardening and shooting hardened cast bullets since about 1978.