Help with one particular bullet mold

[eaglejim101]

I am fairly new to bullet casting, and I am having a terrible time with one mold. It is a Lee mold for a .45-70 caliber 500 grain bullet for my antique Springfield trapdoor (die 457-500). I am using certified 30-1 alloy in a small bottom pour melting pot. No matter what I try, the bullets come out terrible, full of wrinkles. I have raised the temperature up to 800 and higher, I have raised and lowered the height of the mold from the pour spout. I have also closed the pour spout to pour slowly, and opened it up to pour faster.
I also cast .50 caliber bullets for a .56-50 spencer and also cast a .44-40 for my antique Winchester 1873. I have no issue with either of these, but they are Lyman steel molds, and the Lee mold is aluminum.
I clean all three dies exactly the same, so I don't know if it is because of the aluminum vs. steel, or what?
I would sure appreciate any input you experienced casters could provide.
Thanks, Jim

[Larry Gibson]

Use a Lyman or RCBS dipper. With the bottom pour the alloy is just not getting into the mould fast enough for that large a bullet. I use a Lyman dipper with most bullets of 300+ gr for just that reason.

Larry Gibson

[eaglejim101]

Thanks for the reply Larry. I was going to add that I use a hot plate to heat up the mold and keep it warm. But I found that I have to leave the bullets in the mold for at least a minute and a half, otherwise I take a chunk out of the bottom when I cut the sprue.

[cbrick]

In all probability it's as simple as your statement of using and being accustomed to steel molds. Steel holds heat far better than aluminum. With aluminum cooling so fast you need more mold heat (mold heat, not pot heat) to get and keep the mold up to temp. Also try pre-heating the mold on a hot plate. Don't admire your new creations while casting because while you are the aluminum is cooling - Fast. Keep the mold closed and full as much as possible. Cast faster.

Aluminum is a fine mold material but it does cast differently than iron or brass molds. It just takes some getting used to.

Rick

[Bigslug]

I've had pretty good luck with Lee's 405 grain hollow base, which, in theory, because of the base pin, should have similar problems to the added mass of your 500 grainer. I'm running a bottom RCBS pro-melt regulated with a PID keeping it at 760F.

The mold likes to be run fast - it's aluminum and there's not a lot of it, so the heat tends to bleed quick.

You might try loosening the sprue plate just a touch. That might help the air get out more effectively. The Lee molds are not vented, so that could be your problem.

[John Allen]

Some of my 45/70 molds work best if I pressure pour. You do this by putting the sprue right against the spout.

[eaglejim101]

Rick, thanks for the suggestions. I do pre-heat my molds on a hot plate. If I cut the sprue too quickly with this mold, then it takes a small chunk out of the bottom of the bullet. From what I have read, that means you are cutting the sprue too early, so I let the mold sit for about a minute and a half before cutting the sprue and removing the cast bullets.

[eaglejim101]

Thanks, I will try loosening the sprue plate a little bit. One thing I do not like about this mold, is that there is no set screw to hold the sprue plate at the position you want as in the Lyman molds.

[eaglejim101]

Thanks, I will give that a try as well.

[cbrick]

Rick, thanks for the suggestions. I do pre-heat my molds on a hot plate. If I cut the sprue too quickly with this mold, then it takes a small chunk out of the bottom of the bullet. From what I have read, that means you are cutting the sprue too early, so I let the mold sit for about a minute and a half before cutting the sprue and removing the cast bullets.

Possible that your alloy temp is too high, are you using a thermometer - 700-725 is all that's needed. Sounds like the mold temp also is too high, use a small manicurist fan to blow gently across the mold after filling. Don't let it blow across the top of the pot, that causes much faster oxidation. Then all you need to do is develop a rhythm to keep the temps even and all will be good in the world. :mrgreen:

Rick

[gwpercle]

Try the Lyman ladle. I ran 10 lbs of alloy from my bottom pour in a Lee C312-185-1R mould and every one had some type of defect. Melted them all again and cast with the dipper just about all were keepers...90% were perfect. Go figure. You shouldn't have to wait 1 1/2 mins. for the sprue to harden ...too much heat in either mould or alloy. I didn't use a hot plate...just dipped the corner in the melt for 45 seconds and started casting. Keep working with it, you will find out how the mould likes to cast.

[country gent]

I cast mostly 400-550 grn bullets 40 cal- 45 cal 20-1 alloy paper patch and grease groove, I run alloy at 725*-750* pre heat mold on top of pot. I cast over a propane burner and dutch oven. I do monitor temps with a thermometer. I use an RCBS ladle that has had the spout hole opened up to .200 diameter. Some molds want to be pressure poured others want to be poured into. Another thing I do is pour a long sprue keeping it molten as long as possible. I fill the ladle angle the mold and fill emptying the ladle slowlyletting the excess run off the side/front. I get very consistent wieghts and sizes this way and very nice shiney bullets. Try a ladle lyman or RCBS and over pour the sprue keeping it hot longer. Will allow gases to get out better. Make sure the mold is clean oil waxs or other cruds in the cavity will cause wrinkling also.

[eaglejim101]

I did several things, including lowering the temp of my alloy down to 730 to 750, opened up the screw on the sprue plate to allow more air to escape, and raised the mold closer to the pour spout.
I believe that because the alloy was too hot, which prevented me from cutting the spure as it did not cool fast enough, which also resulted in the mold cooling more than it should. Hot alloy in cool mold was causing the wrinkles. Instead of waiting about 90 seconds to cut the sprue, I am now cutting in about 30 seconds. I also keep the mold hot on a warming plate.

In any event, I thank all of you whom provided some insight and ideas, and helped this novice caster overcome a problem. Looking back now. it only requires some common sense in analyzing the situation, combined with some experience and knowledge. Who said you can't teach an old dog new tricks, especially with an experienced trainer?
Jim