Sunday, April 17, 2011

Annealing Lead Alloy for Softer Boolits - Final Hardness Results

To the new folks, there is a description of the Annealing test in the 2 prior posts.  To the regulars, welcome back for another visit.  Now, to the test results:

The hardness continues to increase, at a rate much like air cooled WW alloy.  After 14 days it's up to 12.5 BHN.  Annealing works incredibly well, for a week or two.  That's something to keep and mind and will aid you in making use of this information in the future.

For an afternoon plinking, it's probably not worth the effort.  For an event, or for a test day at the range, it can make a huge difference. 

Freezing the annealed bullets is a way to keep them soft for a longer period of time.  Testing the effectiveness of freezing is in the plans, so stay tuned for more analytics, charts and results.

Sunday, April 10, 2011

Annealing Lead Alloy for Softer Boolits - First Results

For background on this test, please read the prior post.

The cast bullets used in this test were annealed for 30 minutes at 450 degrees.  The oven was turned off, with the bullets inside, until cooled.

Here is the data in chart format, click on the chart to see it full size:

This particular air cooled wheel weight alloy tested as 10.4 BHN, the day after casting.  A bit hard, but in the range of modern day wheel weights.  After six weeks and just prior to annealing they tested at 14.2.  Immediately after cooling they dropped to 8.2.  That's a pretty big drop in hardness.  After 7 days they age harden back to the 10.4 as-cast hardness.

I plan to test them again next week to verify just how they continue to harden.

It's a nice surprise that the hardness dropped to 8.2, just what I had hoped for.  As you can tell, they don't stay there long.  If you cast & load with a just in time approach, this can be very helpful.  If you cast thousands of bullets to be loaded over the next year, you can still anneal in smaller batches, as needed.

It's encouraging to know that the wheel weights can be softened.  The consistency and accuracy achieved in a 357 Magnum with softer lead is measurable and noticeable. 

I plan to roll this new-found-knowledge into my current casting-handloading-shooting schedule.  Currently I cast 5-10 lbs of a given bullet, let them age for 2 weeks, lube & size them.  At that point they are ready to load then shoot.  Usually lasting for 2-4 weeks.  That's with 2 different bullet designs going, shooting 200-250 total rounds a week it works.  Now I'll anneal-lube-size a week in advance for bullets that need to be a softened up.

Hope this helps and gets you to 1 ragged hole at 25 yards.

Monday, April 4, 2011

Annealing Lead Alloy for Softer Boolits - The Approach

Since my supplier of pure lead is drying, the problem is how get bullets of BHN 8 or less casting with wheel weights.  Softer lead bullets provide consistent accuracy, as compared to BHN 11, or 16 or harder.  A well designed bullet, sized to perform in your revolver (often .360 works, but some revolvers vary) can produce great groups, even if it's a harder than BHN 8.  However, softer alloys produce better groups, and do it more consistently.

Strange as it sounds, the process to soften wheel weight alloy bullets is much like the process to harden them.  The difference is, to soften the bullets, they don't get quenched in cold water.

The goal of the upcoming test, is to verify that bullets can be softened to BHN 8, or as close to it as possible.  If they can be softened, does it last more than a few days or does it last for weeks.  Since it takes a long time to verify test results, it will be about a month before I can post the resulting data.

The process is to heat the bullets in the oven, then turn it off and let them cool to room temp.  It can take a couple of hours to cool slowly.

The initial results will be for pure wheel weights, additional tests will verify the impact of adding additional tin.  Which is reported to soften the bullets even more.  Pretty great if it all works out.

The planned test will:

1) Heat bullets in the oven, set to 450 degrees, for 30 min
2) Turn it off, let the entire oven with bullets inside cool to room temp
3) Test the bullets hardness before heating, after heating and then at 7 day intervals
4) Report the results here

To achieve the best accuracy, shooting a softer alloy makes all the difference.  That is, in 357 magnums of course.  Not that I'm closed minded, but it is the most fun caliber to cast, handload and shoot, bar none.