Always heard to use pure lead to mold jigs.
Can wheel weights be used to make flawless jigs if fluxed?
Yes, but it depends on the jig.
Wheel weights are not good for small jigs or those with intricate parts but for my bigger saltwater stuff it isn't a problem.
You do have to sort them first tossing the steel and zinc ones. Then clean out tons of dross and clips after it is melted.
I have a big pot just for melting scrap. I also have a magnet on the end of a bent piece of all thread for removing the clips from the pot.Once fluxed and cleaned they are ingotized.
Only clean fluxed ingots go into my shop to be made into jigs and sinkers.
They are also good for bigger sinkers.
Iv'e used a few hundred pounds of wheel weights over the years. Anymore I only use them if they are free.
Around here wheel weights are hard to come by as so many people make saltwater sinkers out of them.