Anyone else have voids in sides of bullets?

[igolfat8]

Does anyone have these voids in the sides of your bullets like this?


It happens with nearly every cast with 1 or 2 bullets in each 5 or 6 cavity aluminum pistol bullet mold. There is no rhym or reason which cavity will get it. I’ve been fighting this issue for a long time and it seems to happen more in molds without lube grooves.

I’ve thought my alloy might not have enough tin so I added more tin and that didn’t make any difference.

So today I finally figured out the root cause of the problem. It has to do with the speed that I fill my molds with lead. If I open up the needle valve on my bottom pour Lee pot so it flows full volume this causes the voids. I think it might be filling too fast and trapping gas that is unable to vent out quickly enough. When I slow the lead flow to a very slow flow, I get NO voids at all. It’s that simple.

This may be common knowledge but if it’s not then I hope this may help those who were struggling like me.

[sureYnot]

I find I can cast some pretty poor alloy if I give the mold a little shake while it's freezing.

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[Springfield]

Try a faster casting rhythm. Works for me, and I use mostly 5 and 6 cavity moulds. If the mould is hotter the lead will not cool fast enough to trap air.

[Calamity Jake]

Yap, you figured out what was causing the voids, trapping air!!!

[bosterr]

Way back in the 70's, I ladle poured and which ever boolit was poured second got voids like that. I slowed things way down and found success. I've since gone to a bottom pour pot.

[Grmps]

try pressure pouring to see if the problem goes away.

[Oily]

Interesting that all the voids in your examples are in the same location. Your examples look like boolits cast from a single cavity mold with contamination in the cavity. Also the bases don't seem to be square. I see small voids and maybe contaminants in your boolits that suggests you might have a dirty alloy. Your slowing the pour has fixed your problem but I would flux your pot and see if the problem goes away IMHO

[reddog81]

Is that from an NOE 358-135 HTC mold? I had the exact same problem with that mold. I cleaned / opened up slightly the vent lines and that fixed the problem. Air was getting trapped in the mold

[igolfat8]

Is that from an NOE 358-135 HTC mold? I had the exact same problem with that mold. I cleaned / opened up slightly the vent lines and that fixed the problem. Air was getting trapped in the mold

Yes it is. I have the same problems with Accurate and MP molds and to an often lesser extent with Lee molds also. Its not contaminated lead or cavities. I've casted from 700*-750* and have settled on 750* for most of my casting work. Temperature is stabilized using a PID. It seems when I pour slower it allows the vents to work. So that's my story and I'm sticking to it ... for now

[jsizemore]

The rule of thumb around here was to cast at 100degF above liquidus. Since you tried a higher amount of tin plus high heat you end up patchy spots like on the top, just above the crimp groove, and bottom, close to the meplat, boolits. A lower temp, like 100degF above liquidus, will keep the tin in the alloy or if you need to cast at a higher temp, keep your tin percentage below the antimony percentage. This will get the frosty surface about eliminated depending on your casting pace/mold temp. Some folks like frosty so it's your choice

[country gent]

If the mould has vent lines make sure they are clean and clear, Look very close at that location on the mould. I have used a scribe and square to cut them or cut them a few thousandths deeper by hand. Doesn't seem like a lot but it can cure air pockets giving a little more room for air and gasses to flow. Another thing is to experiment with the pour try dead center, on edge and with mould canted a littleA fast full fill that fills the sprue hole may cause air locks also.

[Traffer]

I had that problem recently with a home made core mold. I did not put vent lines in it. The next time I used it I heated the lead higher and went faster keeping the mold hotter. That seems to have cured the problem.

[CJR]

In addition to the comments posted. Raising the lead temperature, to get better quality CB, is typically an indication the lead flow is being throttled/slowed/cooled before getting into the caviiies and producing CB defects. I'd suggest checking the sprue plate diameters and enlarge them to be about half(1/2) the CB diameter or slightly less(NRA recommendation). In other words, enlarge the sprue hole diameters gradually working up to the limit of about 1/2 the CB diameter, stop when the defects disappear. Likewise, If the sprue holes don't have a channel connecting them, add a channel (NRA recommendation). These two things will speed up the molten lead flow into the cavities, minimize CB defects(i.e. improve CB quality), and allow casting at slightly lower lead temperatures.

Best regards,

CJR

[igolfat8]

. Another thing is to experiment with the pour try dead center, on edge and with mould canted a littleA fast full fill that fills the sprue hole may cause air locks also.

Thanks for the tip but I tried that and it did not make any difference.

[sureYnot]

Had same problem with one of my pots. The difference between the pour being too fast or too slow was less than an eighth of a turn of the adjustment screw.

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[Beagle333]

Is the sprue plate too tight? Is it loose enough that if you shake the mold while empty, you can shake the plate open?

[igolfat8]

Sprue plates are tight on all molds.

[BK7saum]

Some recommend to lightly break the top edge of the mold with a stone/fine file where the halves meet to alloy air to better escape as the mold finishes filling. Also, sprue plates being too tight to the mold top keep it from venting as well. If you loosened the sprue plate slightly, this may also help with the trapped air voids.

[fredj338]

I have this issue from time to time with 4-6cav molds, iron or alum. I pretty much pressure cast & find that if I stagger the pours, front, back front back, I avoid the weird phenom of the void in the bullet side usually. Mostly happens with 9/357s molds. I think it has to do with air trapping or diff in temps as the one cav fills next to one already full? Anyway, seems to help my pours.

[44MAG#1]

The mold will trap air if the vent lines, called vent lines for a reason, is not letting the air escape and the alloy is cool enough to "freeze" before it can push the air out.
Just like an injection mold for plastic or metal needs venting. Proper venting I should say.
make sure the vent lines are clean. Don't try to put more metal in the cavity at a rate that the air cant be pushed put. A slow stream smaller than the sprue hole will let the air out around the stream going in the mold.
The mold and metal must be hot enough to prevent the stream and the metal in the cavity from solidifying because it will then cause a void where the pocket of air is.

Again, I mean no harm, anguish, torture or hurt to anyone by my comment. I am not calling out, trolling or baiting anyone on here. I am just making a statement based on what knowledge I have. Which could be a lot, none or some variation inbetween the two.