My 1/4 oz jigs only weigh a hair over six grams!

No doubt this is being caused by the lead I use; Mostly wheel weights, plus a 34 lb slab of unknown composition (garage sale).
I tried modifying a jig mold but ended up making it useless.
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My second attempt was more successful (1/16 oz jigs) but the heads are not balanced -- one side is slightly larger than the other.
I could just accept the fact that all of my jigs are underweight, but I prefer to be more precise.
Has anyone else dealt with this?