Pin hole during casting

[bronko220002]

Guys I just got done casting about 100 bullets from a new mold so that I could allow for culling from any flaws. I only got a couple with shrinkage lines in them but I got 8 that had pin holes in the center of the base. I pour enough lead (pure lead by the way) to create a good puddle over both cavities.
Searching this some say that the sprue is too cool other say the sprue hole is too small to be able to suck the molten lead into the cavity. This bugs me that I have to cull an otherwise perfect bullet.
What say you.

 

[ETipp]

Guys I just got done casting about 100 bullets from a new mold so that I could allow for culling from any flaws. I only got a couple with shrinkage lines in them but I got 8 that had pin holes in the center of the base. I pour enough lead (pure lead by the way) to create a good puddle over both cavities.
Searching this some say that the sprue is too cool other say the sprue hole is too small to be able to suck the molten lead into the cavity. This bugs me that I have to cull an otherwise perfect bullet.
What say you.

I have an old ML book from the late 70's. In the bullet molding section the only thing I am seeing that causes holes in the center of the base of a bullet are trapped air, insufficient metal in the dipper, or a combination of both. It states to loosen the cut-off plate and use more lead in the dipper.

My guess is you most likely are not using a dipper.

 

[bronko220002]

No friend I am using a bottom pour but I'm sure the same principle applies

 

[ETipp]

No friend I am using a bottom pour but I'm sure the same principle applies

Thought you were. I use one as well.

I did have something happen today that I have not had to contend with yet. Due to the small amount of pure lead I had to cast a few with, as well as what was left in the furnace from before, there was some impurities remaining. Something got down in the spout and was pugging it off. I finally got it cleared and back to pouring again.

 

[Greg_E]

Turn up the heat a little, better if you have a thermometer. Most of my molds like 750 to 800 freedom degrees, and my pot often oscillates between that range. I have a Lee 420 and set the dial just under #4 and trim as needed. Going to a PID control the next time I fire it up.

 

[Greg_E]

Also I've found that heating the molds on a hot plate to around 400 or a bit more makes things work better.

 

[edmehlig]

I use the MR Tourch that I bought from Tractor Supply that was recommended by IdahoLewis. It only takes a minute or two to heat the mold up. It sure does eliminate a lot more of the culled bullets that I throw back into the pot.

 

[HC]

It’s already been mentioned above, the spue cutter is too tight.

 

[bronko220002]

It’s already been mentioned above, the spue cutter is too tight.

Could be as its a brand new mold.
My casting temp is at 725 with pure lead

 

[Greg_E]

I'd raise it up to 750 and see if it fixes the issue.

 

[bronko220002]

Casted some more today but raise temp up to about 775. No more pin holes.
One other thing I tried this time - a tip from IdahoLewis. I had the corner of the mold setting in the pot as the lead heated. When the lead got to temp. I opened up the spue all the way and filled both cavities uo 5 times then started casting. Not a single cull bullet!

 

[HC]

Great news. I love it when a plan comes together. Like Lewis says cast um HOT!