Advice for MP hollow base molds

[cwlongshot]

Again, LEAD TEMP is NOT YOUR ISSUE!
Lead temp is probably better closer to 700° but you do you. When your suggested more temp to MOLD we mean hot plate or more casting to bring temp up IN YOUR MOLD.

Adding a hot plate is the single BEST THING that a guy can do to improve there experience and save on his HAIR!!

CW

[Bigslug]

I run almost everything in the 750-800F range for pot temperature, but as has been stated, hollow point and base molds often need a little more. The trick is to have alloy AND mold temperature high enough to where the metal isn't freezing before the cavity fills. As I stated in my earlier post, I'm using rendered shotgun slugs with a tiny trace of antimony as the base alloy, and will drop a few ounces of tin into the 20# pot to get it to behave, but it certainly does not need anything you'd consider a "tin rich" mix.

It's worth considering lowering quality control standards a little bit for these. It is, after all, a soft alloy, self-sealing, low-velocity, shoot-Jerry-in-the-face-at-20-feet sort of handgun. Obviously a clean base and no major voids are still requirements, but a minor wrinkle here and there won't cause problems for what one does with a Webley.

[vagrantviking]

Again, LEAD TEMP is NOT YOUR ISSUE!
Lead temp is probably better closer to 700° but you do you. When your suggested more temp to MOLD we mean hot plate or more casting to bring temp up IN YOUR MOLD.

Adding a hot plate is the single BEST THING that a guy can do to improve there experience and save on his HAIR!!

CW

I'm using a hotplate and got the mold hot enough that the alloy wouldn't freeze in it. The mold was over 650F at that point and I kept pouring as it cooled with the voids continuing.

It must be a weird shrinkage effect with the high temperatures. Under 700F the bases tend to be better but the lube grooves don't fill out on the outside so I'm going to try more tin to thin the alloy and hope that maybe there was a persistent oil contamination or something that prevented fill out in the grooves.

It's just perplexing that the things that work in nearly identical molds don't work for this one.

[Bigslug]

I've definitely had the same (probable) shrinkage voids at the pointy tip of the base pin. I'm not sure there's really a lot that can be done about that one. Bullets will shrink toward their center of mass as they cool, and the center of mass for the MKII bullet is probably right in front of that base pin. Comprehending the dynamics of how lead cast into that shape behaves when surrounded by two dissimilar mold metals is WAY above my pay grade, but that void has never caused me any notable kind of problem in the 100 year old stone axe it is launched from. Work toward a good exterior, and if the base void remains a tiny swirl, forget it and move on.

[vagrantviking]

I do realize that the effects on actual performance are likely little to nothing but it's become a puzzle I want to solve as much as a necessity. I'm also casting for others and want them to be happy with what they see.

Hopefully a hot mold and cooler lead will be closer to the right comprise.

Thanks for the ideas and encouragement ( and the reminder to keep it in perspective).

[Gobeyond]

You can get a 50 lb pot. Do an internet search for commercial lead furnace. Big and quality.

[cwlongshot]

Sags and droops and poor fill out can also simply be a not seasoned enough mold. Can also be MOLD heat issues

Did you heat cycle before first use?


You need to clean the mold. Read degrease. The heat cycles "bake out" the oils and manufacturing fluids. Sometimes this takes 4 or more times but always clears this up. YES it can be done simply using the mold but your on that road and obviously not happy with the journey. Some will suggest dipping a corner of the lold into the lead. This heats the mold helping "cook out" oils.

650 mold temp is EXCESSIVELY HIGH and can lead to damage.

Another problem with running lead temps so high is integration of undesirable alloys. Like Zinc. It takes 800+ Lono melts mid 500's coww 600's. Tin a little less. Constant stiring keeps desirable metals like antimony & copper & tin integrated. They do not "like" each other.

I have hundreds if molds and cast dozens of HP versions regularly. Zero issues once properly seasoned and up to temp.

CW