First brass mold advice

[gman50]

today was my third casting session with the 477-640 brass MP mold. Before use I cleaned the mold with Dawn and hot water. I preheated the mold on my hot plate then allowed it to cool. Did this 3 times. Preheated before use and ran the alloy temperature at 700 deg to start. Made about a dozen cast before they started dropping wrinkle free bullets. Problem was they were frosty on one side to the point that the bands were not sharp. Before today's session I recleaned the mold and did the heating on the hot plate and cooling cycles. Today it didn't take as long to start dropping good bullets. I am still getting the one sided frosting which leaves the bands without a sharp profile. Alloy is 70/30 WW/PB . I tried my pot temperature From 700 to 750. I know this is a quality mold and I'm probably going wrong somewhere. Would it help to make a cover for my hot plate with a thermometer to heat this mold to a specific temperature? Appreciate any guidance here. I've castes for many years but first time with brass mold.

[dale53]

My brass Mihec moulds have not been a problem for me. However, my "standard" alloy is WW's+2% Tin. I suggest you add a bit of tin. If that is a problem for you, you might raise the temperature a bit (725-750 degrees or so).

Good luck!

Dale53

[ohnomrbillk]

I'm with Dale53

They seem to like to cast as hot as can be

[jsh]

Had the same problem. I kept bumping the heat a little at a time. That pretty much cured it. I had mine on the hot plate also. It just wouldn't get hot enough on the HP pins and had to take pliers to the bullets to get them off.
I ended up taking a little LP torch and waving around on the pins. Finally got them warm enough where they would drop off.
Had an incident with my thermometer and am going to have to check it out in the lab at work. But with this mold it was showing 775-780.
My 45-270-SAA mold likes to run hot also.
Another reason I need to get moving on getting or buying a good PID. Casting is a lot like reloading. Takes a little work to figure the quirks of each mold.
Jeff

[2 Dogs]

To get my Miha molds to temp, I submerge the corners of the mold until my melt no longer sticks to the mold. I do the same to the sprue plate.

[dale53]

You want to be careful not to get the molds too hot. You can actually solder bullet metal on the mold. I was experimenting a few years ago with an iron mold. I dipped the corner in the melt until the blocks were the same heat as the melt. I soldered bullet metal in the cavity...

I believe I was lucky to get all of the metal out by heating and wiping. You can also warp blocks. That's something I haven't done but it has happened to others when they overheated the mold.

My current technique is to use a hot plate (the steel covered type of burner rather than a calrod unit) to bring the mold just under casting temperature then bring it up to temp with one or two casts.

When I first started using Mihec's hollow point molds, I had trouble with the bullets sticking on the hollow point pins. I then applied a light coat of mold release to the pins and VOILA! the problem ended. Now, the bullets just fall off the pins when I open the mold.

FWIW
Dale53

[gman50]

Thanks for the tips from all. I failed to mention that I do have 2% tin added to the mix. I believe between preheating and running a higher alloy temp it caused the bullets to drop too frosty with the bands not filling out sharp. Yesterday's session produced better bullets but my mold wasn't quite hot enough at the start. Getting close to finding the sweet spot. Brass vs Aluminum is a very different animal for sure.

[sixshot]

I also dip just the corner of the mould into the molten alloy to pre heat the mould. Sometimes I use a hot plate if using multiple moulds. I've quit using the penta pins, harder to work with & the HP's are more fragile on game although that can be a plus on deer for some people. I'll stick with the round pins.
I always run my furnace on the hot side, up around 800 because I don't add extra tin so it needs the extra heat for good fill out. I've always had good luck using a 70/30 blend of WW & lead for HP's. Powder coating also helps, acts like a poor man's GC.

Dick

[jsh]

I will admit to getting my alloy to hot. Then not waiting long enough for it to set up in the mold. When doing an eye inspection and the driving bands are all distorted from being pulled to soon, I backed the heat down a bit.
The LBT 41 mag mold threw me a fit this time. I cast about 200 and they ended up being all culls. They just would not fill out the driving bands quite right. This mold tends to like heat and tin. I was lacking on the tin I am sure. Oh they would probably have shot, but so would a rock. The more I cast the more anal I get about culling. If it isn't eye perfect it's a cull.
Jeff