Casting temp with 20:1 and a big boolit

[mac266]

For the 20 or so years I have been casting, I've either used wheel weights or Lyman #2. Both are hard enough for pistol loads, and even many rifle loads, especially with a gas check. But lately I've been casting big boolits for black powder cartridges, so I decided to grab some 20:1 so it would be softer.

Normally, I set the mould on top of the warmer while the lead is getting up to temperature. Even so, the first few boolits I drop out go right back into the pot. The mould temperature simply isn't hot enough to cast without some wrinkles. This even works with my 500 grain .45-70 boolit.

However, with my .50-70, the mould simply wouldn't heat up enough. I kept getting wrinkled boolit after wrinkled boolit, no matter my cadence, etc. Wrinkled boolits generally indicate it is too cool, so after I couldn't get the mould warmed up enough, I turned up the dial on my pot to 800. I don't have a lead thermometer; I simply make adjustments to the pot based on what is dropping out of my mould.

This seemed to do the trick. I got a nice batch of boolits for my antique .50-70.

Has anyone else noticed 20:1 lead has to be cast at a higher temperature than harder alloys? This was also the first time I had used that mould, so perhaps it is something unique to moulds that large?

[centershot]

Well, 800*F ought to be hot enough for 20:1 alloy, I only run 725 for pure lead. And yes, 20:1 will require more heat then something like WW alloy. There are a couple of things to consider; First, try pre-heating your mould on a hotplate. This will save some time and you'll be making good bullets sooner. Second, buy or build a P.I.D. temperature controller. No matter how much you hover over a thermometr you're NEVER going to control the pot as well as a P.I.D. will. With a P.I.D. you'll know exactly what the pot temp is and it will be held at +/- 5* F, or so.

[country gent]

I cast 20-1 for big long bpcr bullets at around 725* I cast a 45 caliber that is 550 grns in weight.
Are you bottom pouring or ladle casting?
I find I get better results and consistency ladle casting, with a modified lyman or rcbs ladle. The spouts have been opened up to .205 in size from 3/16. This gives a much faster fill of the mould.
It may not be your temp is to low but the fill is to slow for the temp.

I normally cast with 2 moulds in tandem.
My pot is gas fired and holds 120 lbs when full.As stated above I run 725*on the pot. The large mass smooths out temp swings.
I pre heat the 2 moulds on the warming shelf while the pot comes up to temp.
The first 10 pours go back in the pot automatically.
I dont pour for a sprue but pour the full ladle into the mould letting the excess run back into the pot. I then sit this one aside and fill the second mould the same way. Set #2 down and cut sprue on #1 and refill. BY over pouring the mould like this you keep the bullet molten longer allowing it to pull more in from the sprue. It allows for better off gassing, And the longer pressure aids fill out.

At the end of a session I will have 400 or so bullets all with in .5 grns most with in .3 grns.

If you can try increasing the fill rate.

[Edward]

I agree with country gent except I compression cast ladle held to sprue plate for10 seconds and then remove ladle and repeat/Ed

[Larry Gibson]

With 40.30,20 and 16 - 1 alloys I use 715 - 725 degrees which works for me when dipper casting 300 - 500+ gr bullets.

[ABJ]

See post #3 and 4. Both methods work for what you are doing. I use Country Gent's method most of the time. But! if I have a mold being fussy, then compression casting will solve that problem most of the time. I usually run 775 and up on big boolits using 20:1. Also make sure your vent lines are clean
Tony

[white eagle]

if the mold is new it takes a bit to get the mold into the act of dropping good boolits most of the time
Noticed you said it was your first time using the mold
anyway some take a bit to get "seasoned".

[megasupermagnum]

800f is fairly typical. I'm usually closer to 750f, but it depends on the bullet design. Also, if you were using a bottom pour, definitely try a ladle.

[243winxb]

Maximum pot temperature to start. When bullets are coming out frosted, drop temperature , allow mold to cool, a minute or two. Then cast more. No thermometer needed, ever.

Any where below frosted is ok. In iron molds, frosted bullets will be .0005" smaller in diameter.

In aluminum molds, frosted is not a good thing. Bullets for most part, will be rejects.

[Tim357]

Mike V uses 20:1 exclusively for his BPCR boolits. He sets the mould on the edge of the pot whilst the lead is melting. Once up to temp he runs 15 boolits in a row without looking at them. Then he casts 100 in quick succession. He states he gets at least 100 good boolits every time. Search for his articles in Handloader magazine

[megasupermagnum]

Maximum pot temperature to start. When bullets are coming out frosted, drop temperature , allow mold to cool, a minute or two. Then cast more. No thermometer needed, ever.

Any where below frosted is ok. In iron molds, frosted bullets will be .0005" smaller in diameter.

In aluminum molds, frosted is not a good thing. Bullets for most part, will be rejects.

I can't agree with any part of this post. Maximum pot temp can be 900+F depending on what you have, horrible idea to start there. 20-1 alloy will not frost, so that next part is not helpful. I don't agree with any logic of letting the mold cool before casting. I do kind of agree to a certain extent the idea of starting hot and reducing pot temp as your mold warms up. The shrinkage of your bullet is dependent on the pot temperature, mold temperature, and bullet design. You can't state it will always be .0005", because it won't be. Again 20-1 will not frost, but I can't agree that in mold material has any effect on whether a frosted bullet is good or not. If you are using an alloy that will frost, they can be fantastic quality bullets even from an aluminum mold.

[Carrier]

Some of my best bullets are frosted.

[fredj338]

I cast everything at 750. Try heating your mold on a hot plate.

[rockshooter]

Don't forget it will vary with the temp of where you're casting. My garage is presently 42 degrees, so I run the pot a little hotter in the winter and vary it from there depending on how the bullets come out. Sometimes bullet casting isn't a cookbook thing.
Loren