Bullet casting frustration

[cda4570]

My last casting session has me stumped. I have a BACO 45 500gn gvt mold and a 535gn Brooksmold.
The BACO mold produced good bullets the first time out of the box. It is my first time with Brooks mold.
My pot is a 20 lb Wage control'd by a PID that I built. The PID and lead thermometre are within -+10 deg.
good bullets were cast 20-1 lead at 750 deg the first time I used it with the Baco mold.
I set up with the same alloy and temp to do another batch using both molds. I pre heated them on a hot plate
with the sme 20-1 alloy. This time, no matter what I do both molds throw bullets that have small voids in the lube rings.
I raised the heat in 5 deg steps to 805 with no change. I tried holding the ladle over the mold longer to make sure it was filling the cavity.
I used one mold to make sure it was hot enough by pouring 12 consecutive bullets. Cleaned both molds with carb cleaner and fine steel wool.
Any ideas? I'm a wits end!

[SSShooter]

Could be something in the lead. If you've changed nothing else, will guess you've added lead to the pot, which could be contaminated.

[bruce m]

could pouring technique be an issue?
bruce.

[John Boy]

Flux the melt 2X times and see what the drool looks like

[Lumpy Grits]

Flush clean the mould with brake cleaner before each casting session.
Gary

[Clarence]

In my experience, the CA brake cleaner doesn't work well. Get the non-CA version. Acetone works well, too.

Clarence

[rdnck]

Brake cleaner gives off phosgene gas when it is heated. Phosgene gas causes immediate and irreversable brain damage even when small amounts are inhaled. DO NOT use brake cleaner. Use carburator cleaner instead. Shoot straight, rdnck.

[mdeland]

I use acetone and then smoke the cavity with a shack (wood) match. All you need is a very light coat of smoke you can barely see. This will usually do the trick. If not try adding a bit more tin to the melt.

[kwilliams]

I would try scrubbing out the grooves with a toothbrush/acetone as it seems something is baked in there and is off gassing during the pour.
kw

[Longrange]

Leave the steel wool out of it. Vic

[bruce m]

Brake cleaner gives off phosgene gas when it is heated. Phosgene gas causes immediate and irreversable brain damage even when small amounts are inhaled. DO NOT use brake cleaner. Use carburator cleaner instead. Shoot straight, rdnck.

this is good advice.
phosgene is the gas the Nazis used in their gas chambers.
it is still used to kill the likes of weevils in grain silos.
for both jobs it comes in the form of tablets, which when exposed to air become a gas.
when handling these tablets you need to wear a mask, and gloves, suggesting it not only causes harm by inhaling, but is also absorbed through the skin.
bruce.

[semtav]

For me, 2 things always caused those voids. Mold/alloy to hot, and rotating my mould too fast when pouring.

[Geologist]

I have had this problem with all my Brooks' molds too, and none of my 40 or so molds by other custom mold makers do this. On the other hand, his molds give me the best bases of all. For whatever reason, his molds are the hardest to break-in. Mike Lewis, Paul Jones, and BACO molds cast perfect bullets from the start. It may have to do with the block material.

[MikeT]

I would second semtav's suggestion. Reduce the melt temperature and experiment with rotating the mold slower. Especially if there is "frosting" on the cast bullet.
When I have this problem I reduce the temp and let my mold cool slightly. Then try various "counts" while rotating the mold upright.
This usually takes care of it.

Keep on hav'n fun!
MikeT

[John Boy]

For starters, the best mold cleaning agent is Micro-90® Concentrated Cleaning Solution. Order a free sample and use a business name for the order
https://www.ipcol.com/cleaners/micro-90
* Mix a 5% solution and clean the mold 2x times with hot water and a tooth brush - wipe it dry
* Do Not smoke the mold cavities
* Then flux the melt 2x times stirring the flux deep into the melt so the only dross is a gray/black powder
* Bring the temperature up to between 680 to 730 of the mold and melt ... every mold is like a woman, it likes a different a temperature.
Hot molds cause frosted bullets
Ladle pour with a good sprue puddle on the plate accordingly:
* Tilt the mold about 45 degrees to allow air to escape in the cavity and start pouring - Harry Pope recommendation
* Do a 5 second pour of the melt with the nose of the ladle in the sprue hole with the mold in a vertical position
* Do a 5 to 10 second wait to let the melt harden depending on the bullet weight
* Tap the mold handle bolt ONLY with a wood stick to allow the mold to open
Open the mold halves and let the bullet drop - within 3 to 5 bullets, you will have perfect completely filled out bullets and a flat sharp bullet base
Maintain a constant casting rhythm and the Bell Curve of the bullets will be within a 0.5 to 1gr difference