Avoiding Mold Damage

© Thomas Dugas – 2006


This article covers the prevention of damage to a bullet casting mold, their care, and proper use.  I received a damaged two cavity Hensley & Gibbs Mold #50 as a result of an eBay auction in October 2006.  To my disappointment, a previous owner had ruined the mold by attempting to add additional venting to the mold cavities, and by allowing the mold to become further damaged in a critical area, the projectile base (the base had a sharp nick in the metal which was reproduced in the as cast bullet as a notch).


Modifications of this type (the additional of supplemental venting) are often a fatal cure to a disease known as improper bullet fillout.  The symptoms are rounded corners on the as cast bullet in areas that have a right angle or corner.  As every caster eventually learns, good bullets have nice sharp corners when you are in the casting “zone” .


The correct cure for improper bullet fillout is to adjust mold temperature, alloy mix, or alloy temperature.  Rarely should the owner attempt to correct this condition by altering the mold itself.  It has been posted numerous times, in numerous ways, by innumerable casters, that molds sometimes display a “personality” and require additional care to discover their preferences for temperature and alloy mix.  The devoted caster should carefully adjust those variables other than the mold in an attempt to cure the problem.  I own a 4 cavity Hensley & Gibbs bullet mold that for some unknown reason, will not cast perfect bullets until I allow it to heat up to the point where bullets are uniformly frosted in appearance, and then allow it to cool gradually back to the good casting “zone”.  Once it cools, it will cast perfect bullet after perfect bullet for hours or as long as my arms hold out.  Other Hensley & Gibbs molds I own do not require this overheating to work properly.  It’s a mystery to me why this method is required for this mold, but I learned about it by reading other casters experience on the Internet.


As you can see in photo 1 &2 (click on the photo for a larger version) the addition of crudely scratched vent lines is evident on the mold face.  Photo 2 shows damage to the bullet base area under the sprue plate.  Photo 3 shows the matching notch in the cast bullet created by the nick in the mold base.





Age of the mold does not factor into the damage.  Care and use of the mold is the indicator of its current condition.  If you carefully use the mold during your stewardship (aren’t we all stewards of these fine molds?) then you can pass on to other casters of a future generation as fine an instrument as you used.



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