Question about water quenching wheel weights

[whisler]

I have started using the pencil hardness method for checking my alloy since determining that my 9 mm needs about 13 BHN alloy to avoid leading, at least with my powder of choice. I was a paint chemist and am quite familiar with how the test is performed as it is a common test in that industry.

I decided to water quench some wheel weights to use, and sized withing 24 hours through a Lee sizer die, since I had read that they will harden quickly and become hard to size. After 1 week, 2 weeks, and 3 weeks the boolits were only checking 13 BHN. I thought this was strange since I knew the alloy was wheel weights because I processed them about 2 months before. I chalked it up to use of recycled lead for wheel weights and wasn't too concerned because I only needed 13 BHN any way.

About 3 weeks later, I checked the boolits again and they now check 20 BHN. I didn't think it took 6 weeks for water quenched hardness to kick in. I got the hardness that I expected but in 6 weeks not a matter of days. Anyone have any idea what's going on here?

Edit to add: These were all clip-on wheel weights and were water quenched from the mold. Pot temperature was approximately 725 deg.

[tazman]

With most lead alloys that will harden, you don't get the maximum hardness until some time later. It usually takes between 10 days and two weeks.
A lot depends on the specific alloy and wheelweights are notorious for varying alloy.
There is a sticky on the site that discusses this.

[whisler]

Thanks Tazman

[243winxb]

The higher the percent of antimony , the faster bullets harden.

Mold to water , not as good as oven to water.

[hockeynick39]

Exactly 243winxb! I use a little oven for my rifle boolits and PCing certain other boolits. Works perfectly and I don't have to worry about any water getting into the casting pot!!!!!!!

[Sig556r]

Mold to water , not as good as oven to water.

If his pot is at 725F then solidify to mold (probably 300F temp drop the most) prior to water drop, how is that less potent than water quenching PC bake out of a 400F oven? just asking,,,

[243winxb]

The bullets dont all make it to the water at the same time, when dropping from the mould.

Its not only temperature thats importent, its how long the bullets are in the oven.

See "Example" near bottom of page.. https://patents.google.com/patent/US5464487

Lyman FAQ also has info on how to oven heat treat alloys..

Mold to water accuracy was not as good as air cooled in 45 acp target loads i tested. Alloy was all from the same pot.