Personally, I never did use recycled WW's. Hard to get them, in Detroit, even forty years ago. Most tire shops had agreements with others, in place.
I just used whatever lead based metals I could acquire. Father was a tool & die trimmer. Tool and die moulds were tweaked by casting a pretty hard lead alloy into the dies. Alloy shrunk very little and allowed the trimmer to adjust/trim the dies based on the casting.
When I was young pre-teen, I use to make sinkers, have a lot of Do-It moulds, still. Dad would bring home the sprews. They were oval, about 1 1/2" long, 3/4" wide and 3/8" thick. Over the years, I had cast a lot of sinkers. Use to bank fish on the Detroit River. Made a lot of 7 ounce bank sinkers, way more than I needed.
Friend and I would take the $.25 DSR bus ride, couple days a week to fish, the river at the Belle Isle bridge. The foot of Jefferson Avenue and Detroit River, was the end of the bus line. Happens, that there was a bait shop, when the bus stopped. Crawfish and crawlers were sold, in addition to minnows. Driver would sit there, for a while, before the return trip. Back then they allowed us to carry our tackle and even fish home without any hassle. Belle Isle was where thy did the Gran Prix races, years later.
Later, graduated to strictly artificial lures and had not much need for sinkers. However, I started my bullet casting hobby, about then. So I just melted down most of those sinkers, I made over the years, into bullets.
That alloy was pretty hard. I had no way of measuring it, besides the fingernail test. I developed my own unscientific method. I knew RCBS moulds were calibrated with Lyman #2 alloy and weight was proportionate. So I cast bullets out of the mould and weighed them for average. I added pure lead, gradually, to get the bullets to drop to advertised weight. Came up with my own ratio and duplicated it. This was in the mid 70's, no internet , no forums, no mentors. Trial and error.
I'm still using some of that alloy. I've always tried to recover my bullets. I leased property, back in Michigan, to hunt on. There happened to be an exposed sand ridge. Perfect to set up targets and catch bullets. Dug them out, once a year, and recycled them. When I built in Arkansas, I had a truck load of river sand brought in, by the guy that did my septic, and dumped in a pile to create a sand berm. As a result, I still recover my alloy.
When I get lazy, or need specialize alloy. I purchase lino from Roto-Metals, to add to my pure stash. Pure is about the cheapest lead one can purchase. I use different ratios, based on need. Varies from 3-1 to 2-1 (pure to lino) but mostly it's the 3-1 ratio. When harder is need, I will heat treat. Over the years, my recovered alloy, stays pretty constant. BHN, measured by LBT tester, is about 13-15 air cooled after three weeks. Works for me.