Mold tuning questions.

[Murphy]

Howdy Men,

Although I've been casting for close to 20 years, I've never read anything on how to 'tune' a bullet mold.

Up front, I have more Lyman molds than anything. Single, double and four cavity molds to be exact. I only have 2 four cavity molds...so those wouldn't be as important for as learning about 2 cavity molds. As for single cavity molds? I have probably no less than 5 hollow point molds. The Hollow Point molds are Thompsons #358156 & the #429215 and #429244. Keith style #358429 & #429421. I also have one very special mold that I picked up 'new in the box' a couple years back, but only used once to see how well the boolits would look. I paid a Kings ransom for it...Lyman #311041 Hollow Point.

So talk to me guys. How do you tune a Lyman mold?

Thanks,

Murphy

[Calamity Jake]

The first thing I do to a new to me mold no matter the make is remove the spru plate and use a good machinest stone on the top edges to remove any burrs, then seperate the blocks and do the same to each half around the outside edges always pushing the stone toward outside so there are no burrs on the block faces then I put a very small bevel on the mold top where the faces come together, this helps venting at the top under the spru plate, being careful not to push burrs in the cavities.
Then the mold is degreased and cleaned using brake cleaner and old tooth brush, next the spru plate bottom is worker over with the stone and then polished with 320 wet or dry on a very flat surface(plate glass) this will sharpen the spru holes as I polish, then it's cleaned with brake cleaner.
In the past I have put a light coat of Midway mold prep on the spru plate bottom and mold top to prevent gauling and lead smearing(removeing any mold prep that gets in the cavities with a Q tip and brake cleaner) now I use bullshop spru plate lube, this stuff works great!!

Now I put the mold together and do some casting, if the boolets drop easy, I'm in good shape, if they don't drop pretty easy then there are burrs in the cavities, I let the mold cool then take it apart and under magnafication use an Xacto knife to very carefully remove any burrs from the parting line.

The above is done to all my molds being extra careful with alum.

[44man]

When you have the sprue plate off, make sure you take a fine file and round off the outer edges, then polish with 400 paper. An easy way to deburr the cavities is to swipe the edges with a Scotchbrite pad until you can't feel a burr with your finger nail. It won't hurt the mould.
I keep putting off getting some Bullplate lube, I am broke for a while. I use Rapine mould prep with good results but sure plan on getting the Bullplate.
Thats why I started making my own moulds! I use scrap and the only cost is about $5 for three feet of oil hardening rod. I can make a lot of cherrys with that.
Here is a properly prepared sprue plate. I have made thousands of boolits with this mould with zero damage and these moulds are made with aluminum and the plates are stainless.