Another Newby question

[kbstenberg]

Recently i have been having a small problem when I'm casting.
Why when a bullet cavity is getting filled with lead do i sometimes get a geyser of lead comeing back out of the cavity, rather than filling up an making a puddle. I usually get the normal excess sprue puddle but occasionally i get lead spewing back out of a mold.
Just guessing. I have to work at getting the stream of lead better centered in the hole to fill the cavity.
Almost all the time when i get the geyser, that bullet will have a pinhole void in the base of the bullet.
Only 1 of my molds has this problem an its an older Ideal 429421.
Kevin

[Calamity Jake]

Recently i have been having a small problem when I'm casting.
Why when a bullet cavity is getting filled with lead do i sometimes get a geyser of lead comeing back out of the cavity, rather than filling up an making a puddle.Only 1 of my molds has this problem an its an older Ideal 429421.
Kevin

The melt is hitting the bottom of the cavity and bounsing back causing that geyser. Try tilting the mold a little so the stream of lead hits an angle at the bottom of the cavity, or let the stream slide off of the side of the countersink around the fill hole.

[Linstrum]

First off, try what Calamity Jake suggests, he's a veteran caster with many years of experience.

All the lead geysers I've had are from two things:

1. Petroleum based oil or solvent left in the mould cavity that vaporize and make gas that pushes the liquid lead back out. When liquid petroleum like mineral spirits and oil boil in contact with molten lead they aren't explosive like water, they rather gently produce white smoky gas and bubbling in the lead.

2. Not having adequate venting. The air has to get out before the lead can go in and any trapped air will expand greatly and push the lead out.

In either case, your particular mould seems to have a venting problem and if it were my mould I'd cut new vent lines. I have done that with probably half my moulds.

One wrong assumption many folks make is that when you buy a new mould that it is perfectly made and flawless but that just isn't true!

To cut vent lines I use a jeweler's hack saw and guide it very carefully with my fingers to cut straight grooves about 0.025" wide and 0.010" deep. I usually put in around six lines and I also cut an "X" on the underside of the sprue plate to get a good sharp heel on the boolit, having a well-formed heel is extremely important for getting gas checks to crimp on tightly. Good sharp castings are also important for getting uniform weight from one boolit to the next.

I hope your lead coming back out is as simple as having a little oil in the cavity. The mould should be totally free of oil and grease, except for specific lubes made for moulds.

If you get wrinkled boolits and have poor mould fill-out, read this thread from 11 months back:

http://castboolits.gunloads.com/showthread.php?t=63033

Good luck and do not hesitate to ask more questions or send a PM (private message).


rl821

[lwknight]

Maybe you are just pouring too fast? If you use a melting pot and its not adjsted to flow properly it can gyser up with some molds. Its actually bouncing off the spru plate from the edges of the hole.
I get that sometimes when the pot is full.
I bet you notice a lot less gysering when the lead level gets lower.

[kbstenberg]

Thank you all.
I must add to my first post.
It only happens at the end of the fill of the cavity. About the time the sprue puddle would form. It is all so cavity specific. On the mold it is the closest one to the handles of a 2 cavity mold. The bullet is usually well filled out except for the pinhole in the center of the base. It also isn't constant, but it does happen about every 5th or 6th cast. Which kind of indicated either the lead stream was hitting the cavity hole or i was tilting the mold in some way. As i cast i let the mold rest on the mold guide on my Lee Pro 4/20
Also the sprue puddle is non-existent. There is always a depression where the puddle should be.
Sorrie most of this wasn't in my first post
Kevin

[qajaq59]

It is all so cavity specific. On the mold it is the closest one to the handles of a 2 cavity mold. Check the venting on that cavity.

[lwknight]

Its the way you hold the mold and the stream is hitting the side of the hole. Also too fast of a stream will add to or do the same thing.