Gas trapping on modified mold?

[Chainsaw.]

So someone here started a great thread showing how they took a lee 32 mold and machined it down to make a cheap 32 acp mold. I follwed suit and had a friend whos and ok machinist knock a little off the top of my mold. When I got it back from him I noticed he didn’t scribe in cuts on top if the mold, inder the sprue plate grooves to let the gas escape, kinda figured he wouldn’t understand that part. So I ran it and it sure seems to be holding gases. Every 3rd or so bullet will have a big bubble in the side of it. Am I correct in assuming this is the gas not being able to escape? Any ideas on how I could cut in some gas lines? Im not gonna let him have another stab at it.


Btw, bullets drop at 77 grains.

[Taterhead]

Could start with by cutting a little bevel in the corners of the mold blocks where they mate. Would give air a passage out from under the sprue plate.

[jcren]

Molds didn't have vent lines that long ago. It will work, just a bit pickier about things like sprue plate tension and pour technique. I did just what taterhead described to my molds without top venting and it works. Just dont take too much or you get little fins on the bullet base.

[bosterr]

Slow down the pour.

[country gent]

You can bevel the edges as described above. Use a fine hard stone or very fine jewelers file. A small combination square and scribe can also be used to vent the top. you need a just visible line (.002-.005 deep) A sharp fine pointed scribe with the squares straight edge will cut very nice clean lines rotate square to each side using the 45* side. and make 2-4 passes along it with the scribe. When done lightly stone with a fine stone to remove the light burrs raised.

I would also recommend checking the faces vent lines to make sure they are open and good. Depending on clamping pressures and material they may have been slightly distorted.

[Dragonheart]

The above are some good suggestions. I would add maybe loosen the sprue plate slightly. Try going a little hotter on your alloy so it stays molten longer.

[Conditor22]

More tin.

[mattw]

I have one of these as well. I love it, but it has a quirk. The mould blocks are now so small that no heat is held. Cast fast and I run my alloy around 710 when using that mould.

[Chainsaw.]

Ill try some of these guys. Including slowing the flow. As far as tin, I always run lots of tin, thats not a problem.