Softening wheel weight
Posted: Sat Feb 16, 2008 8:13 pm
When you drop WW bullets out of the mold, they air-cool fast enough to harden slightly. Small bullets will air-cool faster than big bullets. If you have a fan blowing on your casting area, it will speed cooling and increase hardness. One caster was getting 16+ BHN on his air-cooled bullets while using a cooling fan, but if he turned the fan off, the BHN dropped several points.
I used BaBore's hardness tester to measure a few wheelweight bullets. These slugs were air-cooled and had been sitting on my desk for a couple of weeks.
280 gr air-cooled WW -- 13 BHN
418 gr. air-cooled WW -- 12 BHN
Then some of these same slugs were baked in the oven at 430°. After one hour, the oven was shut off, but the slugs were left in the oven so they would cool very slowly. The idea was to anneal the metal, undoing any heat treatment.
oven-annealed WW -- 9 BHN
9 BHN is exactly what the Lyman handbook lists for WW.
Inevitably, I heat treat all my wheelweight bullets whether they need it or not, but if you did want a soft wheelweight bullet for reliable obturation -- like for BPCR or for CAS -- oven-annealing may be worthwhile.
I used BaBore's hardness tester to measure a few wheelweight bullets. These slugs were air-cooled and had been sitting on my desk for a couple of weeks.
280 gr air-cooled WW -- 13 BHN
418 gr. air-cooled WW -- 12 BHN
Then some of these same slugs were baked in the oven at 430°. After one hour, the oven was shut off, but the slugs were left in the oven so they would cool very slowly. The idea was to anneal the metal, undoing any heat treatment.
oven-annealed WW -- 9 BHN
9 BHN is exactly what the Lyman handbook lists for WW.
Inevitably, I heat treat all my wheelweight bullets whether they need it or not, but if you did want a soft wheelweight bullet for reliable obturation -- like for BPCR or for CAS -- oven-annealing may be worthwhile.