Casting minie balls

[mac266]

I recently bought the Lyman .58 caliber minie ball mould for my original 1861 rifled musket. Last night I finally got the pot out and cast a pile of boolits using lead smelted from stick-on wheel weights (the softest lead I have). As normally happens when I cast, the first few went right back into the pot because the mould wasn't heated up enough just yet, but after a while they started dropping out nicely.

They were bright, shiny, fully filled out, and no frosting. In fact, this was the best batch of boolits I've cast in a while!

After they cooled and I was able to handled them, I discovered that more than half had air pockets right inside the skirt at the top, right where the pointy thing goes to make the hollow base shape. More than half!!! They all got culled to be remelted and cast again later.

I assume this is either a temperature problem, or a technique problem. How do you all prevent this?

[dondiego]

Your lead and mold have to be very hot for minnies and you often need to pressure cast or use a dipper but always a large sprue if you aren't pressure casting. If you are using soft lead as you should be, you you won't see frosting. Frosting is related to antimony in my alloys. I have added a small amount of tin to minnies also to help fill out. Less than 0.5%.

[mehavey]

Do not pressure/contact pour hollow-base Minnie balls.
Guaranteed air entrapment. (honest)

Instead... free-pour with spout at least a 1/4" above the sprue
plate to allow air escape as lead enters the mould body....
and leave a puddle.

Let us know....

[BLAHUT]

I use pure lead for mine, so far no problem and I pour so the air can come out.

[ABJ]

Easy fix, just tilt the mold a little sideways when starting the pour and rotate to straight up as you finish with a large sprue. The hole is caused by the lead hitting the pointed part of the hollow base pin. Also make sure your vent lines are clear. Single edge razor works great for chasing the vent lines.
Tony

[dondiego]

Easy fix, just tilt the mold a little sideways when starting the pour and rotate to straight up as you finish with a large sprue. The hole is caused by the lead hitting the pointed part of the hollow base pin. Also make sure your vent lines are clear. Single edge razor works great for chasing the vent lines.
Tony

That's how I pressure cast as well. I make sure that the mold is almost filled and then apply the pressure. Works for me.

[GregLaROCHE]

When I first cast them, it was the first time I cast pure lead. It was a lot harder to get good fill out than when I had casted using an alloy with tin. Next time I plan to add just a bit of tin and see if the boolits come out too much harder.

[stubshaft]

Easy fix, just tilt the mold a little sideways when starting the pour and rotate to straight up as you finish with a large sprue. The hole is caused by the lead hitting the pointed part of the hollow base pin. Also make sure your vent lines are clear. Single edge razor works great for chasing the vent lines.
Tony

That and you have to cast fast to keep the pin hot enough to insure there are no voids.

[Gobeyond]

Wouldn’t 40:1 also be a good idea?

[bedbugbilly]

Keep your pot hot - keep your mold and base pin hot - the first few will likely go back in the pot, but once you get your casting cadence up, you'll get good ones. Pour, cut sprue as soon as you see solid leas on the sprue plate, twist the base pin and pull as you drop and then put the pin in and pour another - you know the routine - it's just a matter of stepping it up a little. My 575-213 has been dropping good ones since the early '60s. You'll have it down in no time.

Enjoy that 1861 - the '61 is probably my favorite model of rifled musket. The one I tarted with was an original '61 model Watertown Contract - lock plate dated 1864. That humpback hammer just seems to make the '61 a classic.

Have fun!