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Texasflyboy
11-02-2006, 09:16 PM
Folks, one of the benefits of flying for a living is that sometimes you get time to just type away on a laptop in the lonliest of places. This is my latest creation. You can also read the article at the Hensley & Gibbs Bullet mold reference website. This is a work in progress and I will add to it from time to time.

Cheers.

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Avoiding Mold Damage

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 the links 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.

http://users2.ev1.net/~eastus1/Casting/HGDamageV2_files/image001.gif

Link to Larger Photo (http://users2.ev1.net/~eastus1/molds/damaged50_1.jpg)

http://users2.ev1.net/~eastus1/Casting/HGDamageV2_files/image002.gif

Link to Larger Photo (http://users2.ev1.net/~eastus1/molds/H&Gdamaged.jpg)

http://users2.ev1.net/~eastus1/Casting/HGDamageV2_files/image003.gif

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.

MT Gianni
11-04-2006, 11:10 AM
Great read. I have found better base fillout with some of my molds comes from a looser sprue plate. A too tight plate can resist bullet fill out. Gianni.

9.3X62AL
11-04-2006, 12:10 PM
GOOD ARTICLE, TFB!

I concur with Gianni's method, also.

montana_charlie
11-06-2006, 01:03 PM
The PGT loaner mould I used had a chip missing at the base corner, much like in the picture. It was very small, and manifested itself by leaving a tiny 'tit' sticking out of the base corner. I just trimmed each bullet with a razor knife. I'm glad it was not my mould, and it illustrates the fact that those loaner moulds saw some abuse as they passed from hand to hand. The first one that came to me was so warped the faces only touched at three corners. (Probably caused by improper pre-heating...)

Venting under the sprue plate can be improved by just 'breaking the corner' of the mould halves from the cavity out to the edge of the mould. You can do only one side if you wish. The 'groove' should be so small you almost can't feel it when dragging your nail across.

A tight sprue plate promotes galling, wear at the pivot, and squashes the tension out of the wave washer. Adjusted so that a 'slinging' motion of moderate force causes the plate to swing about a quarter open works well, and will be a bit looser when the mould gets hot.
(I only use single cavity moulds. An adjustment this loose might not be right for multi-cavity blocks...I dunno.)

As to the quality and usefulness of the article...
It is well written, and accurate...as far as it goes.
I think some mention should be made about how not to preheat moulds, and something about protecting them from rust between casting sessions.

Warping and pitting can destroy the 'instrument' as completely as unwise modifications.
CM