alloy varriation in pot?

[acsteve]

Just sized a hundred or so 460-350gr RD boolits, noticed some required much morre effort to size than others. Is this common, sloppy mold operation? or does the alloy vary with in one 10lb pot. Did stir it when it was fluxed but pored 3lbs or ww alloy.

[Ricochet]

I'd be more suspicious of variations in as-cast diameter. There are a lot of ways this can happen, mostly involving the mould not being consistently closed. I find that especially problematic with Lee 6-hole moulds.

[Linstrum]

As-cast diameter variations from the mold not closing consistently from one boolit to the next would be my choice, too, since it is hard to see 1/10,000-inch difference in diameter between two castings but the difference can be felt quite easily in the sizing operation.

Another thing is the difference in hardness due to differences in cooling rates and metal temperature at the moment of pouring the alloy into the mold, and the mold temperature itself. Those can easily lead to a bit of difference in hardness that can be felt during sizing, although not as great as the difference between boolits quenched by dropping into water and others just left to cool in the air. Those differences in hardness tend to disappear after a few weeks, though, so if old boolits have differences in how hard you have to pull on the press handle when sizing them I'd still choose slight differences in the order of a few 1/10,000 of an inch in diameter as the cause of any variations felt in press handle pull.

[nemo]

What type mould ? If iron/steel , look for burs along boolet cavity with 10x glass ,I use a stone or a sharp knife(hobby). oil lighty hingepin, Lee moulds ,use lube on mould joints an pins thats best marks on slugs,1cold,oil,cooked old oil ..you can use mach smoke,pensel lead num2 best. Nemo

[Bass Ackward]

Were you water dropping?

[44man]

Bass asked a good question! The time change from pouring to dropping in the water can change the hardness a little between boolits. Maybe a stuck boolit that just won't leave the mold?
Also the time the first air cooled boolit is dropped to the last one dropped. If you cast for a few hours, the first cast can be a little harder then the last.
Get the mold so hot it expands a little more will also give a slightly larger boolit. Get it and the lead way too hot and boolits can shrink more. Colder cast can be a different size and hardness.
Guess what I do? I ignore it. :drinks: I just try to keep things even while casting.
If you shoot BR, pay more attention!
Also the 10# pot doesn't hold 10#. You are always changing the temp by keeping enough lead in it. I like the 20# pot and one casting session with a ladle will empty it.
Guys that cast all day keep another pot with melted lead in it to add to the casting pot.
HOOOO BOY, why don't we just shoot jacketed? :groner:

[Freightman]

Use a thermometer! will keep the lead at same temp. have more than one mould and rotate.

[Orygun]

Just sized a hundred or so 460-350gr RD boolits, noticed some required much morre effort to size than others. Is this common, sloppy mold operation? or does the alloy vary with in one 10lb pot. Did stir it when it was fluxed but pored 3lbs or ww alloy.

Another thought.....I use a Star sizer and if I don't run through a lubed boolit between every 20 or so, they get harder to size. Also got the base heater a little too warm one time and could not push one through until it cooled.

[crowbeaner]

I'm with ricochet; I'd suspect differences in as cast diameter myself. I cast some 300 gr. 45 bullets last summer and they were hard to size because of the linotype I used. With alloy closer to #2 they were easier to size to .452. The gaschecks went on easier too. Lino will cast really uniform bullets if the mould is hot; you have to really preheat it if iron/steel. Don't waste time between pours if you are quenching with water; I make sure the bucket is well away from the pot and drop them straight in. My $0.02. CB.

[grumpy one]

While variation in as-cast bullet diameter is possible if there is something wrong with the mould or the casting technique, my experience is that the dominant effect comes from bullet hardness. I have found that my water-dropped bullets vary in hardness from 14.3 BHN to 24.8 BHN, measured one year after they were cast. Alloy was 3% tin, 5% antimony. I have also found that three weeks after casting, hardness of air cooled bullets varied between "shiny cast" (mould hot enough to cast but not frosty) and "frosty cast". The shiny cast bullets ranged from 20.9 BHN to 31 BHN, while the frosty cast bullets ranged from 12.1 BHN to 16.6 BHN. In that instance alloy was 1.3% tin, 5% antimony.

Bullets with medium antimony content (5 to 7% range) seem to be highly sensitive to cooling rate. If you stay below 3% or above 10% this sensitivity is likely to be much less. My solution, for what it is worth, is to slowly air-cool all such bullets after casting them in a very hot mould, then heat treat them if I need them hard. 5% antimony bullets, with either 1.3% tin or 3% tin, have fairly uniform as-cast hardness of about 14 BHN if you do this. If you don't want to have to worry so much about quality control, stay with straight WW plus tin (i.e. about 3% antimony), so the cooling rate sensitivity is less. You can heat treat WW bullets to make them very hard, if you need to.

[acsteve]

thanks, I'll pay closer attention to temp. If I set a lee pot on a temp setting, will it hold it, or do I need to constantly adjust it? I ususually give the pot an hour to heat up the lead, then flux, stir and start molding. It is usually 700 degrees when I start and goes up slowly as I mold. I try to keep it under 750 degrees.

[grumpy one]

The Lee controller is not really a thermostat, and is remote from the molten metal anyway, but if you have a constant setting and a constant level of metal in the pot, the metal temperature will be constant after a stabilization period. As the metal level in the pot falls, the temperature rises with a Lee.

Remember that constant metal temperature in the pot does not mean constant metal solidification conditions. The mould temperature has a bigger effect on the bullet hardness than the metal temperature does, because it has a bigger effect on how quickly the metal cools through, and just below, the solidification temperature.

[TCLouis]

think you will find it is a function of boolit doiameter.

Next session look at those that size slightly harder . . . I would almost be willing to bet that they will appear to be sized more on one side.


My standard Lee 38X150 SWC is bad about this or has been the two sessions where I have used it.