Wednesday, March 9, 2011

Initial test results: Casting at 725 VS 925 degrees. How bad is casting hot????

So this topic has been bothering be for some time.  I've often heard concerns of what happens to WW and other bullet alloy when casting with a hot pot.  So it was time to run a test.  I also wanted to figure out how to soften WW to meet my needs in my 357 magnums.

Added for clarification:  There is a popular idea that casting with a hot pot cooks out the tin and antimony from the WW alloy.  If that happened the alloy would be softer.  Their follow on argument is that a hot pot oxidizes out the tin and antimony, some cliam within minutes. Again, if either point is true, the alloy will become softer. 

Added:  How to harden and soften cast bullets using heat is an upcoming topic.  However a few other projects are first.  A much closer look at H110 in the 357 Magnum is not-to-far-off.

I figured I'd cast test bullets at intervals (see below) and measure the BHN after 1 day, 7 days and 14 days.  After 1 day I'm shocked enough to post the first results.

The test scenario is straightforward:

The 725 degree test and then the 925 degree test are identical:
  1. Clean out the pot
  2. Put in 3 lbs of WW
  3. Bring the lead to 725 or 925
  4. Cast 4 bullets - minute 0 of the test
  5. Cast 4 bullets - at the 30 minute mark
  6. Cast 4 bullets - at the 60 minute mark
  7. Cast 4 bullets - at the 120 minute mark

725 BHN results after 1 day:
    0 min = 10.4
  30 min = 10.4
  60 min = 10.4
120 min = 10.4

925 BHN results after 1 day:
    0 min = 10.4
  30 min = 10.4
  60 min = 10.4
120 min = 10.4

There is no negative impact on BHN from casting with a hot pot. 

My goal of wanting to cook WW down to a softer BHN isn't going to work out.  I'll wait a week and see if results change at all.  But I didn't expect them to be 10.4 this quickly and don't foresee them getting much harder, if at all.

The next time someone tells you the horrors of casting with a hot pot and the major impact of oxidizing tin etc... and having a major negative impact on the bullets, you don't have to take their word for it.  You don't have to take my work for it either. The test is easy, try it yourself and see what your results are.

I plan to continue casting hot as I find it to work well.  Now that I know for a fact there's no negative impact on the alloy, there's no reason to be concerned at all.

Update:  Here is a snippet from the  Lyman Cast Bullet Handbook, third edition, page 43.  The tin and antimony doesn't cook out of the lead.  It's apparently difficult to remove enough tin / antimony to matter. Cooking 2 hours at 925 oxidized out some tin possibly, but it still measured 10.4 BHN, it made ZERO difference.

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