cavities/bubbles at the base?

[troy_mclure]

im pouring from my new lee 10lb pot, into my lee 2 cavity mould. melting down unlubed pre made boolits.

i get decent fill out, but i keep getting bubbles/cavities at the base of the bullet, off to the side of the sprue hole.

any fixes/ideas?

[BABore]

Make sure the mold is hot enough and pour a more generous sprue. Too much Bull Plate lube left on the sprue plate will cause some small acne on the base, but eventually burns off.

[pdawg_shooter]

Sounds like a venting problem.

[armyrat1970]

im pouring from my new lee 10lb pot, into my lee 2 cavity mould. melting down unlubed pre made boolits.

i get decent fill out, but i keep getting bubbles/cavities at the base of the bullet, off to the side of the sprue hole.

any fixes/ideas?

Make sure your mold is clean. Use mineral spirits or denatured alcohol. I use the alcohol for a new mold and then just clean with toothpaste with really hot water and rinse well, before each casting session. I dry and heat them up over my kitchen stove. I try the mold without lubing or smoking first. If problems arise I lube them lightly and smoke the cavities. Make sure no lube you put on the mold is getting around the cavity base, or under the sprue plate. And yes, make sure you fill the sprue hole. A little over full won't hurt.

[94Doug]

....and make sure you are giving it enough time before you open the sprue.

[troy_mclure]

mold is hot enough, it doesn't cool the lead as i dip it in.

mould was cleaned with mineral spirits, then smoked.

ill try scrubbing the sprue plate, see if that helps.

[fredj338]

mold is hot enough, it doesn't cool the lead as i dip it in.

mould was cleaned with mineral spirits, then smoked.

ill try scrubbing the sprue plate, see if that helps.
I don't think it's mold temp or a dirty mold. I get theses occasionally in the middle of a perfect run. I think it just happens. Try casting w/ the sprue plate tight to the spout then backing off to make your sprue when the mold is full. I call it pressure casting.

[454PB]

Too much pressure, which is filling the mould too fast. Try opening the valve less, or keep the alloy level lower in the pot.

You may have already noticed that the problem goes away when the pot is down to half full or less.

[thx997303]

When I have this problem, I loosen the sprue plate. Works well.

[troy_mclure]

i think i got it, i was fitting the hole in the sprue plate to the spigot on the pot.

with a gap i get no bubbles, but plenty of spillage.(slow reflexes!)

[DLCTEX]

You need to pull the mould slightly away as you end pressure pouring so that you leave a puddle to draw from as the metal cools and shrinks.

[armyrat1970]

i think i got it, i was fitting the hole in the sprue plate to the spigot on the pot.

with a gap i get no bubbles, but plenty of spillage.(slow reflexes!)

There you go. A little spillage isn't bad but if you are a scronger, like most handloaders and casters, you will want to save that spillage, and throw it back into the pot. It takes practice and time before you can really learn how to fill the sprue, so to speak. I have a new Lee 20# I am still getting used to. The placement of the spout is giving me heck with my old eyes. Sometimes I don't fill the sprue and have problems with base fill. When I over fill with a little spillage, no problems, and just throw the over spillage back in with the sprues.

[saskgunowner101]

Does your pot have an adjusting screw to increase/decrease the flow? If so, restrict the flow to slow it down when the pot is full and give it a little turn if it slows down too much while casting. My pot is the Lee 4-20 and I'll be damned if I didn't learn this until after casting a couple hundred bullets.:D

[steg]

I had the same problems with a Lee mold, I was holding it right up to the spout tight. But then after I tried leaving a little gap, about 1/4" and keeping the melt on the hot side, cured the problem, boolits are frosty, and alot of spillover, but I'm getting alot better results that way.

I also Lee-mented the mold, it made a world of difference, they drop out nice now.....steg

[Marlin Hunter]

Don't hold the mold level. Tilt it at about 3 degrees.

After both cavities are filled and the sprue is still liquid, rotate the mold so it is level, then tap the sprue plate tang with the wooden dowel until the sprue solidifies.

Holding it at an angle help remove most of the air. Tapping it with the dowel helps remove the last bit of air.

[troy_mclure]

mine drop out nice and clean. no tapping required.

[hiram]

I had dimples form on the base if there was too much bull plate lube on the sprue plate. In a few casts, the dimples are gone. Not a big problem. If the rest of the bullet is smooth, I would think the mold is hot enough.