flawed mini

Oliver Sudden · February 5, 2018, 01:28 PM

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

Chainsaw. · February 5, 2018, 01:41 PM

Your driving bands/crimp groves look a tad round. Could maybe add a touch of tin without getting the lead to hard.

Pour slower?

dahermit · February 5, 2018, 07:09 PM

Preheat the molds hotter still and increase the temperature of your melt. Pure lead needs to be pretty hot to fill out a mold.

res45 · February 5, 2018, 07:13 PM

Pure lead in the pot as well as your mold needs to run a bit hotter than wheel weights or other lead based alloys normally will to fill out well, a little tin wouldn't hurt either. Crank the temp on your pot up a bit and see if they drop any better.

snuffy · February 6, 2018, 12:37 PM

O.S. the rest of the mold might be hot enough, but the base pin is NOT. Also, as noted, the lead itself is probably not hot enough. Pure lead has to be at least 800 degrees to cast decent. Also as said, about 1% tin would make a huge difference on how well those mini's would fill out without raising the hardness hardly at all. Tin doesn't harden lead much, it just makes it behave much better. You'd still get the skirt to expand to grip the rifling with a bit of tin added to the pure.

Make sure you use pure tin. Using lead-free solder from some sources would add antimony which WOULD harden the mini's. Note the fine print on lead-free solder that says "95% tin--5% antimony. It could also say 5% silver or 5% copper, neither would harden pure much, but the antimony certainly would.

Oliver Sudden · February 6, 2018, 02:32 PM

Thanks, I'll try going to max temperatures.

mehavey · February 6, 2018, 05:41 PM

Run pure lead ~780-800dgr
Do NOT* contact pour. Instead pour about 1/4-1/2" off the hole to vent/alleviate the tendency to form an air pocket near the top of the pin.

*(Go ahead. Ask me how I know)

Oliver Sudden · February 6, 2018, 09:57 PM

Made some good slugs today. 850 degree lead, very hot mold and 3/8" from the bottom pore pot. Any other way made voids. Bad part is the stinking mold throws .575" and I need .578 or larger for this rifle. I'll dig out my other mold soon.
Thanks all.

mehavey · February 11, 2018, 08:18 AM

If it's pure lead, it should bump up to groove dimension --- no problemmo at all

jmorris · February 11, 2018, 04:09 PM

The imperfection at the bottom of the one on the right is what I get from a mold that is not up to operating temperature.

Inclusions on the base of the bullet seem to be worse the larger the sprue is.

February 5, 2018, 01:28 PM	#1
Oliver Sudden Senior Member Join Date: January 7, 2017 Location: Colorado Posts: 272	flawed mini 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

February 5, 2018, 01:41 PM	#2
Chainsaw. Senior Member Join Date: September 12, 2015 Location: Issaquah WA. Its a dry rain. Posts: 1,774	Your driving bands/crimp groves look a tad round. Could maybe add a touch of tin without getting the lead to hard. Pour slower? __________________ Just shoot the damn thing.

February 6, 2018, 12:37 PM	#5
snuffy Senior Member Join Date: May 20, 2001 Location: Oshkosh wi. Posts: 3,055	it's the pin O.S. the rest of the mold might be hot enough, but the base pin is NOT. Also, as noted, the lead itself is probably not hot enough. Pure lead has to be at least 800 degrees to cast decent. Also as said, about 1% tin would make a huge difference on how well those mini's would fill out without raising the hardness hardly at all. Tin doesn't harden lead much, it just makes it behave much better. You'd still get the skirt to expand to grip the rifling with a bit of tin added to the pure. Make sure you use pure tin. Using lead-free solder from some sources would add antimony which WOULD harden the mini's. Note the fine print on lead-free solder that says "95% tin--5% antimony. It could also say 5% silver or 5% copper, neither would harden pure much, but the antimony certainly would. __________________ The more people I meet, the more I love my dog They're going to get their butts kicked over there this election. How come people can't spell and use words correctly?

February 5, 2018, 07:09 PM	#3
dahermit Senior Member Join Date: October 28, 2006 Location: South Central Michigan...near Posts: 6,501	Preheat the molds hotter still and increase the temperature of your melt. Pure lead needs to be pretty hot to fill out a mold.

February 5, 2018, 07:13 PM	#4
res45 Senior Member Join Date: September 15, 2007 Location: NC Posts: 753	Pure lead in the pot as well as your mold needs to run a bit hotter than wheel weights or other lead based alloys normally will to fill out well, a little tin wouldn't hurt either. Crank the temp on your pot up a bit and see if they drop any better.

February 6, 2018, 02:32 PM	#6
Oliver Sudden Senior Member Join Date: January 7, 2017 Location: Colorado Posts: 272	Thanks, I'll try going to max temperatures.

February 6, 2018, 05:41 PM	#7
mehavey Senior Member Join Date: June 17, 2010 Location: Virginia Posts: 6,894	Run pure lead ~780-800dgr Do NOT* contact pour. Instead pour about 1/4-1/2" off the hole to vent/alleviate the tendency to form an air pocket near the top of the pin. *(Go ahead. Ask me how I know)

February 6, 2018, 09:57 PM	#8
Oliver Sudden Senior Member Join Date: January 7, 2017 Location: Colorado Posts: 272	Made some good slugs today. 850 degree lead, very hot mold and 3/8" from the bottom pore pot. Any other way made voids. Bad part is the stinking mold throws .575" and I need .578 or larger for this rifle. I'll dig out my other mold soon. Thanks all.

February 11, 2018, 08:18 AM	#9
mehavey Senior Member Join Date: June 17, 2010 Location: Virginia Posts: 6,894	If it's pure lead, it should bump up to groove dimension --- no problemmo at all

February 11, 2018, 04:09 PM	#10
jmorris Senior Member Join Date: November 22, 2006 Posts: 3,077	The imperfection at the bottom of the one on the right is what I get from a mold that is not up to operating temperature. Inclusions on the base of the bullet seem to be worse the larger the sprue is.