Spent the middle part of the day casting 225 bullets for my 32-20 and had more than the usual sludge problems so am swallowing my pride to ask the cause.  I was using certified (BACO) 25-1, casting at 700 degrees.  The catalyst was my dipper; it looks like a lead oxide is forming on it.  I used beeswax every 30 rounds or so, and some if it went back into solution.  Would it make sense to use a dipper other than cast pot metal?  I've not had similar issues using a 50-50 range scrap/linotype metal for my military '06.

Agree

I think your fluxing way too often every 30 rounds?...I use parrafin once before casting, and don't again until I add more lead...
Or the next casting session.

Terry

I use a Lee 20# pot and an old Lyman dipper. I flux with either flaked carnuba wax or powdered rosin. I only flux when I add to the pot whether it be sprue or more allow. I don't have that volume of gunk on the top of my pot. I do agree with the others that your perhaps fluxing too often. I flux and scrape the gunk off the top and keep on casting. On occasion I will get a bullet with some dirt in it, it just gets recycled. 
Sam

I ordered the RCBS dipper.  The dipper I was using was a rough casting and poorly-drilled spout, looked to be a Lyman.  There has been no zinc or other crap metal in this pot, so I figured the sludge was some lead oxide.  I flux with beeswax when the sludge forming on the dipper interfered with the pour.  Hopefully the new dipper will take care of things.

The heretic among us - that's me, it is.

About four years ago, I stopped using casting flux altogether.  After reloading the pot with RotoMetals alloy, I just scrape the sides and stir until a light grey dross rises to the top.  Skim that off and I'm good to go.

So far, there have been no negative effects from not using flux.  Bullets fill out nicely and my moulds remain nice and clean.

JackHughs

bnice wrote on Aug 12^th, 2016 at 9:04pm:


Yes.  I weigh every bullet. I mostly cast a David Mos designed .32 caliber 5-groove bullet.  The alloy is 1:20 and the indicated temperature is approximately 760 degrees.

It takes about four or five castings for the bullets to completely fill out. It takes another six or seven castings to achieve stable weight.  After that, bullet weights vary from 210.8 grains to 211.2 grains.

Most of the weight variance is due to my lack of attention.  I love my Lee pot but it requires constant manual adjustment to maintain indicated temperature.

JackHughs 

I've also stopped using flux, except when I clean up scrap in great big lots, I use marvalux on the initial melt to get the dirt and crud out of it.   

I found that if I put the ingots in my lee pot, let it melt, use an aluminum rod to scrape the sides and bottom, and then skim off the dross, I can cast 30 to 50 bullets before I have to skim dross again.  I use my same ladle that I cast in to skim the dross, and strike off the gunk out of it by hitting it on the top of the discard can rim a few times.  I save the dross, and throw it back in with my initial clean up lead melt.  I think some of it may go back into alloy.

My .38 bullets cast 90% within .1 grain.  My .45 bullets cast 95% within .5 grain.  Most of the rejects are in the first dozen that I cast, that number goes down when I preheat the mold on my lab hotplate.  When I have cast .32, they nearly all fall within .1 grain.  The lighter bullets cast a lot more consistently.