Does Cast Bullet Hardness Change over 3 Months

Does Cast Bullet Hardness Change over 3 Months?

It’s been three months since we cast up a batch of water-quenched and air-cooled bullets as part of our ongoing lead hardness testing project.  Let’s see if they’ve changed.

Method

As with the previous experiments, five bullets from each group will be tested using the Lee Precision Lead Hardness test kit.

Starting with the air-cooled bullets, we’ve got measurements of:

Bullet 10.051″20.1BHN
Bullet 20.048″22.7BHN
Bullet 30.054″17.9BHN
Bullet 40.054″17.9BHN
Bullet 50.054″17.9BHN

For an average BHN of 19.3. That’s substantially harder than the 11.16 they started out at three months back.

Now let’s move on to the water quenched bullets. Our readings here are:

Bullet 10.044″27.2BHN
Bullet 20.044″27.2BHN
Bullet 30.042″29.9BHN
Bullet 40.044″28.5BHN
Bullet 50.045″26.0BHN

With an average BHN of 27.76. Just as with the one month results, these haven’t changed much at all recently, but are still quite a bit harder than the 22.76 we started with.

Results

After three months time, the air-cooled bullets have reached an average of 19.3BHN, while the water-quenched variety have stabilized at about 27.76BHN.

Summary

Once again the hardness of the air-cooled bullets has increased quite a bit. As of three months they’re now sitting at a very impressive 73% harder than they were cast.  The water-quenched bullets have remained fairly static at about 22% harder than cast, though it’s worth noting that there’s been almost no change at all in the last two months.

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