Most clip on weights are about a 12 BHN if air cooled.
When water quenched, and let to sit for a week or so they can be harder. I have never tested it myself.
Stick on wheel weights tend to be near pure lead. Close enough to make muzzle loader balls with. I think somewhere in the area of 8 BHN. They also make good expanding hollow points from what I hear.
I use them to cast .45-70 hollow base bullets for my air rifle. I have not shot them in the air rifle yet, though I will when it warms up in a week or so. For large bore air rifle they have to be very soft, and slightly over sized.
If you are using them for woods defense against bears or large dangerous animals then you may have to add some more tin to the alloy to get a good hard non expanding bullet.
If defending against 2 legged vermin then softer for good expansion is preferred by most.
Do not fall into the thinking that harder makes them not lead up the barrel. Hardness takes far back seat to fit. They should be over sized to the chambers, and bore by at least one thousandth of an inch. Poor fit leads more barrels, that too soft by a wide margin.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.