Third session, new phenomenon and question

[LittleBill]

Today at the end of the work day, I stole some time to cast some more boolits. In my last exciting episode, I was getting some strange craters, which some of you opined might be caused by contamination from the sprue plate lube. Now I've got something new going on with the same boolit. In today's session, I was getting slightly rounded bases from time to time. It was not consistent with a particular cavity, nor was it consistent from pour to pour. The mold was nice and hot, and I was getting good fill out for the most part. But sometimes the left cavity would produce a slightly rounded base while the right had a nice crisp corner, and then they would flip, where the left would have a crisp corner and the right would be rounded. And sometimes both would be fine. [smilie=b: I could see a line around the rounded one every time I knocked the sprue off.

After casting a bunch and letting them cool enough that I could handle them, I grabbed my Mitutoyo micrometer and started checking bases. The rounded ones were measuring a scant .452, sometimes .4515. The crisp corner bases were pretty much measuring .453 - .4525. I have some fuzzy photos below of what I observed. In the first one, the boolit on the left is the good one, and the one on the right is rounded every so slightly. In the second one, there are two good ones on the left and two rounded ones on the right. I was getting a good sprue each pour, and the bottom of all the bases look as nice as nice can be. Any ideas from the wisdom here?

http://i119.photobucket.com/albums/o159/FotoBill/roundedbasecolt02_zps5e44554b.jpg (http://s119.photobucket.com/user/FotoBill/media/roundedbasecolt02_zps5e44554b.jpg.html)

http://i119.photobucket.com/albums/o159/FotoBill/roundedbasecolt01_zps9858c003.jpg (http://s119.photobucket.com/user/FotoBill/media/roundedbasecolt01_zps9858c003.jpg.html)

And yes, I know there is a little flash or whatever on the base of the one. It is probably going back into the soup anyway.

[btroj]

Mould is too hot. An overly hot mould can cause smaller bullets, rounded bands, and the bullet is crystallizing as you open the mould and that causes those little tear pits like on the bullet second from right on the base.

Slow the casting cadence and use a small fan to cool the mould as spruce hardens. In time you will find a cadence for that mould that keeps the mould temp in the right range.

[runfiverun]

notice the rounded drive bands on the same boolits that have the rounded base band.
too much heat this time.
controlling the molds temperature is critical for consistent boolits.

different molds like different things even made by the same manufacturer.
my lyman 2 cavity 375 mold runs exactly the same as my lee 2 cavity 45/70 mold.
my two accurate 30 cal molds run exactly the opposite of each other.

[LittleBill]

Thanks guys. I will cool it down a little.

[cbrick]

I agree that it looks like the mold is too hot. What is your pot temp set at?

Rick

[btroj]

Lee mould, larger diameter bullets means mould overheats fast if you cast quickly.

I use a small fan and blow it across the sprue plate for a set count depending on the mould. Cut sprue, dump bullets, repour. Key is finding the temp that maintains the right mould temp and prevents over heating.

[LittleBill]

I agree that it looks like the mold is too hot. What is your pot temp set at?

Rick

I started with the temperature as measured by my Lyman thermometer just under 700 deg. But that was at the beginning, and I was having so much fun I forgot to check it again. I had cast about 90 200 gr LSWC for my .45 ACP before I started these boolits. I am using a 10 lb Lyman pot and a ladle. The mold was preheated on an electric fry pan.


Lee mould, larger diameter bullets means mould overheats fast if you cast quickly.

I use a small fan and blow it across the sprue plate for a set count depending on the mould. Cut sprue, dump bullets, repour. Key is finding the temp that maintains the right mould temp and prevents over heating.

Ha ha, I was going fast after reading about keeping the speed up so the mold doesn't cool. But, learning the hard way is a lesson that sticks better, and is how I seem to do most things. I can definitely see using a fan, especially when it gets warmer. I am more comfortable in cooler temperatures, and sitting over hot lead starts me sweating. If it helps the boolits too, so much the better. Thanks for the tip. I suppose I could turn the temp on the pot down just a little too.

[btroj]

Each mould will have its own needs. Smaller, lighter bullets need a faster tempo. Bigger diameter, heavier bullets need a bit slower tempo.
Al moulds get too hot faster, brass slower.

Key thing is you learned something important. Now you can observe what is happening and automatically know what to do.

Congrats on learning a valuable lesson

[cbrick]

All electric pots will get hotter as the level of alloy goes down unless it's PID controlled, it's just the nature of the beast. Don't look at it as pouring lead, look at it as pouring heat, 200 gr is a fair sized boolit and a fair amount of heat plus more cavities means the more heat your pouring plus your pot is getting hotter as you cast. Looking at it like this it's pretty easy to get a mold too hot to cast well. The posts you read saying to cast faster is simply because the most common newbie problem is too cool of a mold. Now that you know what to look for it will get easier and better, as with anything new it's nothing more than a learning curve and you now have a worthwhile lesson learned.

Rick