bubbles in my miniballs

[wszumera]

I am trying to cast some .58 cal miniballs using a lyman 575213 mold. I keep getting bubbles in the base of the bullet.

Could those with experience casting, using a removable base plug mold, chime in with ideas on how to get a bubble free bullet?

I'm using pure lead and a bottom pour pot.

Thanks,

Clutch

 

[Many Klatch]

I haven't used a Minie ball mold, but I have a similar problem when I cast a .72 ball.

The problem is that the lead shrinks when it cools. You have to have a puddle of lead sitting on top of the sprue hole so that as the lead inside of the mold cools and shrinks, that there is still molten lead sitting in the pour hole that can be sucked down into the mold to fill the new cavity.

This is a particular problem when using a bottom pour lead pot. The bottom pours are so precise and neat that it real easy to pour a minimum amount of lead on top of the sprue cutter.

If you try pouring using a ladle, and be less neat, you might find that your problem goes away. I finally got to the point with my bottom pour lead pot, where I make a point of letting a little lead spill over on each bullet to make sure that the large balls have a chance to fill completely.

Many Klatch

 

[camo trky]

You need to preheat your mould.It looks like the lead is setting before it fills the mould.I set mine on the side of furnace while the lead is melting.These are big bullets so you might need to preheat your mould with a propane torch.

 

[BrownBear]

In addition to all that, for big bullets or long bullets I like to use either a bottom pour furnace or a Lyman dipper that is shaped kinda like a lemon with a pour spout on the bottom.

With either one (and a hot mould, of course), set the pour spout right against the sprue plate and give the lead an extra second or two to "settle" into the mould, then separate them slightly to form a big sprue before stopping your pour. Watch the sprue for a small dimple to form as the bullet cools inside the mould, then swing the cutter.

I cast Forster-style 12 gauge slugs and an older Lyman 58 cal hb minnie using these techniques, and once the mould is hot enough I never get a void.

 

[paulvallandigham]

I agree with Manny: You have to have your lead HOT before filling those big molds, and you have to keep both the mold and the lead hot during the pour. That means keeping a larger pool of lead above the cut off plate so that the lead in the mold doesn't cool too quickly. You will also get incomplete bottom edges on these hollow based bullets, or bubbles in the edge, which are terrible for accuracy.

Keep that mold hot before the pour, and keep the lead very hot- approaching the temperature at which the bullets begin to frost- to fill the skirts and cool slowly enough to not leave bubbles as you show. Reject any bullet that does not show a complete skirt( bottom edge). After they cool, sort them by weight. That is the easiest and fastest way to find those that have air bubbles in them.

 

[silverfox]

Not only do you have holes but all your skirts are bad. I don't use my bottom pour melter when I am doing larger than .54.
The big minnies need a hot mold and hot lead and they need it quick. Brownbear said he sometimes uses a large lemon shaped bottom pour dipper on minnies. That is exactly what I use as it holds the heat and pours fast. You have to keep the removeable base plugs hot. In a rapine mold with the attached plug once it's hot your ready to go.
Another solution maybe you can or need to open the sprue cutter to a little larger size to get lead in the mold faster. Just a thought.
The main secret to doing minnies is get everything hot and keep it hot.
Fox :hatsoff:

 

[yooper]

I kept havng the same problem while trying to cast mold #577611. I had everything very hot. I ended up taking a needle file and reventing the mold. It works like a champ now.

 

[Bob Riegl]

:grin: I keep a small electric heater operating next to my LEE furnace---and I lay my moulds on that heater in between pours, I find that keeps up the temperature and I generally get good casting results. Your pix indicate that the mould is not hot enough. Try pre-heating your mould to be much closer to the temperature of the lead in the pot. :v

 

[Keppy]

I guess the question I would ask is, do they all look like that? LOW HEAT How many did you try making? I have poured some big bullets and sometimes it takes a dozen or so to get the lead flowing and everything working good. I agree with the rest. Make sure you have a good spur on top. That will pull lead into the mold if it needs it. Good luck

 

[wszumera]

Well I tried running the pot temperature all the way up, pre-heating the mold, even using a propane torch to put a re-heat on the base plug between bullets.

I tried pressure pouring followed by putting a blob on sprue plate and also drop pouring with a big blob.

I checked the vent lines and they look fine.

Nothing gave me a consitantly good bullet though most of the bubbles when I got them were smaller. I would get random big bubbles at times. No pattern to it.

I never could get a frosted look look to the bullet. Normally with an aluminum mold with the temperature turned up I'd be getting that. These iron blocks don't seem to heat up very well.

The only thing I haven't tried is dipper pouring because I don't have a dipper and with a bottom pour pot, I'd have trouble getting a dipper in.

I will give the dipper a try after I buy one. Will have to use a pot on the coleman for that.

Thanks for all the ideas,

Clutch

 

[wulf]

I have cast hundreds of mini ball in a couple of hours..Been doing it since 1959.I learned to also
heat the "pud" The insert that makes the base hollow..If not the lead will cool too fast when it
reaches the hollow insert and make those bubbles.
So as you pre heat the molds also heat the "pud"
insert...The hollow base plug...Works for me..

 

[paulvallandigham]

If your casting pot is old, the thermostat may be about shot. You certainly should be able to get a casting pot hot enough to give you frosty bullets.

Try opening the hole in the pot for pouring out the lead, and even enlarging the hold in the cut-off plate on the mold so that you get more lead into the mold faster. That should cure the problem.

A lot of the casting equipment was made and designed back when everyone was casting .30 cal bullets in the 1950s. They may have to be tweaked to cast these large balls.

 

[arquebus]

About 80% of my casting is with Minies & I've never had much luck with the electric Lee pots when casting them either.....don't seem to get enough heat. Paul's suggestions of opening up the nozzle a bit might help some & checking out your thermostat couldn't hurt, I've known people who have 'tweaked' theirs to get more heat. I ended up going with a propane ring & a cast iron pot (a small Dutch Oven holds a decent amount of lead) & have never looked back. I use an RCBS ladle, though a Lyman would be fine, too, but I'd keep away from the open Lee type ladles as you need the spout & resevoir of lead to build up the pressure to get the lead to fill the mould fully. I also drill out the nozzle hole in the ladle to improve flow. The above suggestions will help aleviate the dimpling you are getting, & will also fill out the skirts properly which you aren't currently getting, however don't expect 100% perfect minies all of the time, it's just the nature of the beast to get a few imperfections occasionally, I probably get about 5% rejects out of a batch but unless they have actual air holes like your examples show I save those to use for fouling shots.
Anyway, to sum up: get a propane ring, a small Dutch Oven, & a RCBS/Lyman-type ladle with the nozzle drilled out.

 

[wszumera]

I have an immersion temperature probe out in the garage. Too late to play tonight but I'll see what the pot temperature is tomorrow and try again.

Just out of curiosity, how hot is hot enough.

Thanks,

Clutch

 

[arquebus]

From memory mine runs about 700 degrees F.

 

[MercerLake]

From your pictures I'd say the lead is cold, and the mold is cold. I run my lead between 800 and 900F measured with a thermo-couple. Preheat the mold by placing the corner of the iron blocks so they touch the molten lead. Don't use a torch on the iron blocks as you may permanently warp them. If you are using aluminium blocks they will preheat much faster than iron, they also cool much faster. With Aluminium blocks use a mold prep from NEI Handtools or smoke the mold cavity and base-plug with a candle or lamp. I use a Lyman dipper with a spout. Leave the dipper in the melt between pours. I hold the dipper above the mold when pouring then place the spout against the sprue hole as it fills, leave a large puddle on the sprue. :grin:

 

[paulvallandigham]

If you are using a dipper, the lead has to be hot enough to heat the dipper, and the mold. If you have a bottom pour casting pot, where the lead will pour directly into the mold, the temperature you need depends on your casting technique. If you put the mold in contact with the spout, it can be cooler than if you allow the lead to drop even as little as 1/2 inch between the spout and mold !

If the mold begins to cast frosted bullets, the temperature is " Hot " enough, but you have to keep the mold hot between pours, and if using a dipper, it also has to be kept hot. When I used a dipper, I let it float on the molten lead while I knocked off the sprue, dumped the bullet, closed the sprue cutter, and put the mold on the top of the casting pot to reheat, while I dipped more lead from the pot. The iron molds from Lyman would heat faster if I put the mold in direct contact with the pot's edge, rather than just allowing the hot air rising off the lead to try to heat the blocks. When you use Aluminum Alloy molds, like those sold by Lee, you have to use a different technique. Aluminum heats fast, but also cools fast. I would put the edge of the blocks into the lead while I filled the dipper, and then pour the lead into the mold after just lifting the mold above the lead in the pot. If you buy two molds, you can alternate them, allowing one to heat up on the top edge of the pot, while you are cooling a bullet in the other one, and removing it from the mold. This works particularly well when using a bottom pour pot.

 

[eph289]

Hey! Bring all your stuff over in the morning.Between your stuff and mine we should come up with a solution.

 

[Keppy]

We have all talked about heat and I believe that is your problem. But in the past I have had problems even with casting a 45 RB. Have you fluxed and stired your lead. Sometimes we forget about that important part also. We have to be sure we mixed it. Like others have said if you can't frost them your not getting enough heat. I have poured frosty ingots with my Lee pot.

 

[wszumera]

Thanks to all of you for the input on my casting problem. Everyone posted good info as I read back through the thread.

I went over to uncles (eph289) and we played with it some more. Uncle cleaned the vent lines that I thought looked okay and found a bit of crud.

I cleaned the mold one more time with a solvent in case there was any lubricant out gassing.

We put a probe in the pot and saw that the lead temperature is running 768- 774 degrees F. This is using Uncles pot. I haven't checked mine yet.

We preheated the mold and plug using a propane torch, playing it all over.

We used a Lyman dipper and that fills the mold so much faster than my bottom pour. We would pour and keep a puddle on top of sprue plate to maximize heat and volume of lead for the mold to suck in when cooling.

Once we were getting good bullets, I tried skipping the step where we gave the base plug a re-heat in the propane torch between bullets.

That got us back into bubble land which went away after we went back to heating the plug between bullets.

We never got any frosting on the mold. Since this is pure lead (we think), I would think the lack of tin or antimony has something to do with that.

The base plug is one I made since the die was purchased w/o one cheap. I'm not entirely happy with how it fits at bottom of skirt, I am tempted to make one out of aluminum to see if it works better. I wouldn't mind thoughts on that idea.

It looks like I need to come up with a way to keep the plug hot, use a dipper, run the pot hot, and think pure thoughts.

Clutch