flawed mini ball

[Phil Coffins]

I'm a fairly experienced caster but can not seem to over come getting a void in the base of a mini bullet. Note the dark half moon in the photo. I have two different molds that produce the same flaw. These are pure lead as they should be and the molds have been carefully cleaned and pre heated. I've tried casting from the bottom pore both touching and not, ladle pore, as I do for my Sharps, with different speeds of pores. Fine looking bullets on the out side and even if the base cavity looks good the weight varies as much as 20 grains. Ideas?
IMG_0251 by Oliver Sudden, on Flickr

 

[BrownBear]

If I'm seeing what I think I'm seeing, the stud or whatever it's called for forming the hollow base was colder than the mold. If that's the case you might have to cast more minies (dump them back in the pot) before it's completely heated and the mold is filling well around it.

 

[Scota4570]

Smoke the mould and base plug.

Pressure cast instead of using a dipper. Hold it on the spout for a good ten count.

Run the lead and mould hotter.

 

[mooman76]

Minies can be a pita especially moulds that have the pin separate from the mould. It's difficult to get and keep than pin hot enough. I have a 54 that I never did get to fill out properly but I gave up quick.

 

[nkbj]

Yeah, that looks familiar.
A second hand hot plate is on my list.
Might tear up an empty bean can and make a little cover to hold back the draft.

 

[rdstrain49]

Yep

 

[Heelerau]

Phil a ver timely posting. I have been casting minnies and pritchetts since about 1972 and in the last couple of months got a kink in my casting swing as they say. Bloody mystifying as after checking for obvious faults I normally get about a 3 to 4 grain variation . I weigh my bullets and group them within a grain for competition, saves flyers.
Now to the point, mould and plug are pre heated as normal on my pots flanged base, lead well fluxed with beeswax. Now I use an old bearing metal ladle, quite large, I hold the mould over the pot and pour in from about 3 inches above the sprew hole and I keep pouring until the ladle is empty. No more voids in the base. I had used to get the odd void in the nose if I did not leave much of a puddle on the screw plate, but the voids up from the base were a real puzzle. Drove me mad for awhile as it was the same with all my minnie and pritchett moulds. I did add about 1 inch of 50/50 lead tin solder as well, but this is not necessary. The other thing make sure you have quite a large aperture in the sprue plate,
Now I am back to casting minnies etc like I always have. I must have started resting the ladle on the sprue and being to neat in not having lead run back into the pot, lesson learned.

Cheers and good luck

Heelerau

 

[Phil Coffins]

Thanks for the ideas every one. I'm going to try some more casting soon and will post the results.

 

[hanshi]

I think Brown Bear is on to something. Big slug molds require a good bit of heat to fill out properly.

 

[Tom Compton]

Smoke the mould and base plug.

Pressure cast instead of using a dipper. Hold it on the spout for a good ten count.

Run the lead and mould hotter.

What Scott said plus pour from bottom pour or ladle w larger hole. I use a HotPot and pour a lot of over flow leaving a large puddle. While the lead in the mold is cooling I put the over flow back in the hotpot using needle nose pliers.

 

[Phil Coffins]

Today's casting went better. Bottom line is 850 degrees, a very hot mold and 3/8" from the bottom pore produced bullets that varied no more then 3 grains.
Thanks for all your suggestions.

 

[fleener]

I cast hundreds of 530 grain conicals in .45 cal each year.

I think a good pot that keeps an even tempurture is important.

I use a hot plate to pre heat my mold, and I also use a dipper. I leave the full dipper on my mold for a 5 second count. I think the head pressure helps fill out the mold.

fleener

 

[F.G. Ford]

Hi,
I have ben casting a long time and have gained a little knowledge on getting the right ball or bullet.
Casting .45 round balls is some what easy, casting minie balls ( bullets ) is another story.
Lead has to be hot, mold has to be hot also, even then you will get cavities.
Getting lead too hot is dangerous to you ( lead poising ) and also produces poor bullets.
To get good minies a small amount of tin helps.
It helps in casting and helps in good shooting.
Keep a cover over the melting pot to keep mold and lead hot.
Also a fan to keep you cool and fresh air for your safety.
On a big bullet you can dip the corner of the mold in the lead to keep it hot.
I would keep away from the high temperatures in molten lead.
Lead melts at 621 degrees F, so 800+ degrees is too hot and dangerous for your health.
For good casting of big bullets, your mold should be close to 650F degrees.
The mold will cool quickly away from the furnace.
Also your bullets/balls should be shiny, if they are frosty they are too hot, if they are covered with wrinkles they are too cold.
All of the above is available and common knowledge.
The long and short of good minie bullets is a hot mold, lead not so pure ( a little tin )and cast slowly.
BE SAFE!
Fred

 

[Heelerau]

Hi,
I have ben casting a long time and have gained a little knowledge on getting the right ball or bullet.
Casting .45 round balls is some what easy, casting minie balls ( bullets ) is another story.
Lead has to be hot, mold has to be hot also, even then you will get cavities.
Getting lead too hot is dangerous to you ( lead poising ) and also produces poor bullets.
To get good minies a small amount of tin helps.
It helps in casting and helps in good shooting.
Keep a cover over the melting pot to keep mold and lead hot.
Also a fan to keep you cool and fresh air for your safety.
On a big bullet you can dip the corner of the mold in the lead to keep it hot.
I would keep away from the high temperatures in molten lead.
Lead melts at 621 degrees F, so 800+ degrees is too hot and dangerous for your health.
For good casting of big bullets, your mold should be close to 650F degrees.
The mold will cool quickly away from the furnace.
Also your bullets/balls should be shiny, if they are frosty they are too hot, if they are covered with wrinkles they are too cold.
All of the above is available and common knowledge.
The long and short of good minie bullets is a hot mold, lead not so pure ( a little tin )and cast slowly.
BE SAFE!
Fred

Fred, I might recant about not using a little tin with my minnies. I shot a couple of targets a short time ago with my original 3rd Model Pat 53 Enfield, I had cast up some Parker Hale Minnies, which are a bit shorter than I usually use but work with with the 1 in 78 twist. I shot an 87 off the bench at 50 yards and an 81 off the bench at 100, These minnies had a tiny amount of tin and they worked a treat.