flawed mini

O

Oliver Sudden

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

Pour slower?
 
Preheat the molds hotter still and increase the temperature of your melt. Pure lead needs to be pretty hot to fill out a mold.
 
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.
 
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.
 
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) ;)
 
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.
 
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.
 
You must log in or register to reply here.
Back
Top