deposits around the edges ?? new to me

[Litl Red 3991]

I've been working a certain RCBS 2-cavity mold pretty hard the last few months. It's been excellent up until the last session when the areas between the grease grooves started showing rough fill out. It was heaviest near the seams.

Looking closely showed what looked like lead deposits. But they seemed to be tougher than lead and were stuck pretty hard. They really didn't want to be scraped out.

Never seen anything like it.

[Dusty Bannister]

Any chance you are running your alloy a little hot, the mold a little hot, and the bullets are really frosty? If you are seeing a lead smear on the bottom of the sprue plate or the top of the mold, that could be part of your problem. If that is the issue you might notice the castings starting to stick in the cavities. Lower the temp or pace and see if that might help. Dusty

[Litl Red 3991]

The alloy is held at just under 700F. All the iron RCBS molds work like magic when the pot temp is just under 700F. Sprue/mold top smears are very seldom. No frost.

The little dots are nestled right into the corners of the GG bulges, right where the molds come together.

[Litl Red 3991]

I've taken the time to empty the present load of lead and start with fresh. I remembered adding some purchased hockey puck shaped slugs recently. Couldn't remember where I'd gotten them but remembered them as pure. That alloy dropped nearly the same BHN, with the same diameter slugs as before and thought nothing of it. However, they were really difficult to size. And there has been an odd "leading." Tiny dots of lead. Not obvious in the muzzle before cleaning, but the first couple of patches have pinpoints of lead spread around.

Weird...

[Bent Ramrod]

I've had that happen with a custom mould. It gave no trouble with higher-melting alloys that were mostly lead. But the Lino-wheelweight mixtures stayed soft or fluid in the mould for a longer time and would tear slightly at the edges of the cavity where the blocks met. The tiny bits of lead seemed to attract more with each filling until it looked like a sort of rough plating along parts of the edge.

Lowering the temperature didn't help that much, because it was a large mould with a large cavity (and, of course, cast like a dream) so the heat, even at lower melt temperatures, would build up until the metal in the cavity was soft or fluid again, and the problem would recur.

The little dotted lines of damage looked even worse since the rest of the castings were so perfect, even along the rest of the barely visible parting lines. I found the best way to remove the lead was coating one of the best castings with Clover 320 and giving it a few turns in the cavity. (This is way short of lapping the cavity; a few turns didn't polish the cavity, just removed the leading.) The condition might be avoided by lowering temperatures and slowing casting rhythm until it goes away, but I don't like casting slowly. The BruceB technique of holding the overheated mould in the breeze of a small fan between fills might also help. I found a slight wipe of Bull Plate Lube on the faces, but not in the cavity, seemed to help. But mainly, I went back to the higher melting alloys for casting in that mould.

[Litl Red 3991]

Thanks for the info. Those deposits surely do make good bullets look bad. I got them out about the same way you describe. The fresh alloy gave no problems in a somewhat short session and the mold appears to have stayed clean.

I have used a small fan before and your post reminded me of it. Although I think the weather might have done so in a few more weeks. The sprue plate seems to be staying particularly hot recently. I must be doing something different or longer.

Thanks again...