bad bases

[two bit okie]

this is a photo of some the bases from my last cast job. bullets are lee 340 gr 45-70 bullets. as can be seen in the pics, there are voids and what looks like wrinkles in the base. these examples were random and can come in the middle of a perfect run. I have tried speeding up and slowing down, change pot temp in both directions.

Please help, I dont have enough hair to pull any more out.

[GRUMPA]

It almost looks like a loose sprue plate as if sometimes it's not laying flat on the mould when pouring the lead. Can you see any daylight between the mould and sprue plate when its closed, or when it's closed can you move the sprue plate up and down?

[Larry Gibson]

Are you ladle or bottom pouring?

Larry Gibson

[lbaize3]

Oddly enough, I get some of those when I:
1. Squeeze the mold handles too hard
2. Have a loose sprue plate
3. Do not leave enough lead on the sprue plate
4. Wiggle the mold about after putting the lead in

Hope that helps you a bit.

[beagle]

Wouldn't hurt to bevel the top edges of the blocks just a bit to give better venting as well./beagle

[Sonnypie]

Once they are loaded, nobody will be able to tell.

Something else, gas checks hide that as well.

[geargnasher]

I have several moulds that didn't vent well until I did what Beagle suggested above, but even before modification I learned how to "swirl pour" the lead into the cavities and control the rate of pouring in such a way that air wasn't trapped in the cavity. A combination of large enough sprue plate hole, pouring the stream to one side of the hole and holding the mould at a slight angle allows the air to purge back out the sprue hole more effectively. Also, if you bottom-pour, shut off your fans and pot for a second so it's quiet, and pour a few while listening carefully to the sound of the lead going in the cavities. If you hear the stream breaking up into droplets and making a rapid "dripping" sound echoing inside the cavity, increase the stream volume. You can create so much turbulence in the mould cavity that all the vents and exits are closed to the air before it can purge.

Gear

[two bit okie]

ok some answers.
1 bottom pour
2 I have wiggled, bumped, shook, yelled at, cursed at
3 tightened the sprue plate,

Same results. and even another question, these blocks dont want to release the bullets even with a double shot of mold release.

[Larry Gibson]

One last question; alloy?

Larry Gibson

[runfiverun]

i'd say the sprue plate is cold.
you could lap the mold to get the burrs out so it will drop better.
if you are fighting with getting the boolits from the mold things are cooling off too much.
i'd fix the dropping problem first.

[Red River Rick]

Are you filling the sprue wells completely, to the point were they are almost overflowing?

Seems like there is not enough lead in the sprue well for the bullet to draw on when it's cooling, hence the voids.

RRR

[Larry Gibson]

If the alloy is correct and the mould, including the bottom of the sprue plate is clean, then i'd say the OP is;

not getting the enough of the alloy into the cavity quick enough. (open up or adjust open the alloy stop to get a faster flow of alloy)

the temp of the alloy and mould are not hot enough. (a ternary [?] alloy should be in the 700 - 750 range for large bullets)

Alloy not hot enough with too small a sprue. (higher alloy temp and large over flowing sprue)

Larry Gibson

[HangFireW8]

Two Bit,

Same results. and even another question, these blocks dont want to release the bullets even with a double shot of mold release.

This is part of the problem. While you are shaking and knocking trying to get boolits out of the mold, it is cooling off. With aluminum molds, this extra cooling time is ruining your boolit quality.

Mass production molds often need careful deburring and cleaning. Even the slightest ledge or overhang at the edge will create monumental release problems. Clean out all the mold release junk and run a pencil tip from the cavity outwards over the edge and feel for the slightest catch. If you can feel it, the boolit will stick on it.

HF

[geargnasher]

Two Bit,



This is part of the problem. While you are shaking and knocking trying to get boolits out of the mold, it is cooling off. With aluminum molds, this extra cooling time is ruining your boolit quality.

Mass production molds often need careful deburring and cleaning. Even the slightest ledge or overhang at the edge will create monumental release problems. Clean out all the mold release junk and run a pencil tip from the cavity outwards over the edge and feel for the slightest catch. If you can feel it, the boolit will stick on it.

HF

+1!!! Mould release plugs up vent likes like no tomorrow! Get some brake cleaner or denatured alcohol and clean ALL of that worthless garbage off of your mould, scrub the vent lines with a toothbrush and do the rest of what HF mentioned.

Gear

[Bret4207]

Bingo! Get that krap outta the mould, it insulates the mould from needed heat, clogs the vent lines, etc.

[beagle]

I'll go with Bret on that one. Clean that mould of all the mould release and it will probably cast well. I have never had the need for mould release in 50 years of casting bullets. A propery polished mould will release and make good bullets without the addition of something else in the cavity.

If you want mould release or are experiencing a sticky cavity, find out what is causing the bullet to stick and fix the bur or whatever is causing it.

If you really must, spray a warm mould cavity with spray moly and then polish it with a soft pine stick until it shines. Then cast like crazy. Eventually all of the moly will wear off except what's in voids and crevices and it will drop really good. You only have to do this process once and that will fix it up./beagle

[epcii]

Does this affect accuracy?

[sav300]

epcii,Hi and welcome

[Bret4207]

Another problem with mould release is making the boolit smaller. Even heavy layers of soot can do that.

[mdi]

In my limited experience, I'd say the sprue puddle isn't large enough (and I agree with Mr. Gibson's last post!), having experiences similar problems with voids in bases. I clean my molds with brake clean and for sticky molds I'll use tooth paste or Comet as a lapping compound to clean up the cavities. If needed I use a very fine valve grinding coumpound, lightly on more stubborn molds. I like to make sure the sprue plates are clean and flat so I'll remove the plate and clean it/polish it up with emery cloth on a pane of glass. I put nothing in my molds except a bit of Bull Plate on the locating pins/rods. Bull Plate also keeps lead smears off the bottom of the sprue plat if I cut the sprues too soon. My clean-up methods have worked on old Ideal molds to brand new aluminum molds...