Voids inside Bullets.

[Colorado4wheel]

I have started to have problems with my bullets “keyholing”. I thought some were slightly undersized because they sized easily. So I was drilling some holes through the base of some good bullets to try and make the molds a little bigger when I noticed that I was hitting some voids. At least that’s how it felt. So I filed a bullet in half and sure enough, small void near the middle. When I cast I seem to need to be at 800F to get good fill out on my Lyman 4 cavity 147gr 9mm molds. I cast using two molds at the same time. I think it may because I sometimes get a pretty slow pour from my Lee pot near the end. Sometimes I forget to open the adjuster on the valve a little more as the pot goes down as well. Both result in the occasional slow fill of the mold. Besides that these bullets look good. Any other ideas? I am using range scrap right now.

[Maven]

2 suggestions: First, weigh all your CB's (I know it's a pain in the butt.), establish an average (mean) weight +-, say 0.5gr., then remelt all CB's that vary from that average wt., especially the lighter ones, as they probably have voids. Second, try casting with a ladle and lowering the temperature to 750 deg. F. You'll still have to weigh your CB's, but you may get fewer rejects with ladle casting, though dedicated bottom-pour casters will argue the point.

[Char-Gar]

Every mold is a little different and often require some changing is how we fill the mold from a bottom draw furnace. Sometime we want the stream to hit the hole direct. Other times we want to hit the side of the spru chamfer and let the alloy circle into the hole. Then often we need to adjust how far the mold is from the spout. You have to try and find out what works best with the individual mold.

I never let the alloy go below half full. I stack ingots on the top of the furnace to get them warm and them add them one or two at a time to keep the level stable. I have never messed with the valve.

You can have internal voids in bullets and that is why we scale our bullets to cull them out. With a uniform casting technique there are few of them, but we still want to hunt them down.

There are other reasons a bullet can keyhole.

[Frank]

You might have a venting problem. Check to be sure vent lines are clear. Lead goes in, gas has to go out. If it can't, you get a void.

[Colorado4wheel]

How whould I clean the vent lines?

[Char-Gar]

Use a scribe with a fine point.

[Bret4207]

Yup, just drag it from the cavity away towards the edge of the mould. DON'T go crazy with that, it only takes a little. I would also recommend you stop trying to use two moulds. I'm betting they just aren't getting hot enough for consistent castings. If you aren't having to slow your pace a bit because you are getting frosty boolits you aren't casting anywhere near fast enough. Mould temp and pot temp are 2 completely different things. If you keep turning the pot up but you aren't picking up the casting pace you are wasting your time. Cold moulds produce wrinkles and voids. Poor venting can produce voids too and venting in a cold mould is slower it seems. Heat is your friend, use it.

[geargnasher]

I agree with Bret, STOP USING TWO MOULDS AT ONCE.

There's a huge problem with doing this: You can't keep either one of them hot enough for good fillout, and that contributes to voids and other imperfections. That's why you think you need to run your alloy so hot, to compensate for the fact that your moulds are WAY too cold. Anything over about 750 degrees for typical boolit metal alloy temperature totally negates the surface oxide barrier effect of tin, and also causes tin and antimony to dross-out of the alloy at a very high rate, which changes the composition in a short time.

What to do? Use one mould, run the alloy no hotter than 700 degrees, and learn the temperature the mould needs to throw the best boolits. Remember, mould temperature controls boolit quality, and casting pace (number of casts in a given time period) controls mould temperature. Alloy temperature needs to be maintained at about 100 degrees over full-liquidus AND MAINTAINED THERE. If your boolits aren't filling out at 100 over liquidus, then you have a problem not related to the pot temperature, more likely a problem with your casting technique.

Gear

[Colorado4wheel]

I should add that the Keyholing is just about 1 in 25 bullets. Not every shot.

I think the keyholing is due to some undersized bullets. I was just surprised to see a void.

[Colorado4wheel]

Using one mold I cast at about the same pace as when I use two. If I go much faster I get a lot of lead smearing and that leads to other issues. I need to let the sprue cool enough before I cut it.

I can get the molds hotter. I have and use a hot plate. I actually use a steel heat sink to cool the molds after I cast for a while. The molds are at 275F when I start casting and get up to about 300F after some time of casting.

[Ben]

Keep a damp sponge handy and hold it to the sprue plate about every 4th or 5th time you open the mold.

This will help keep the sprue plate cutting the sprue instead of smearing it.

Ben

[725]

Try a little bull plate lube on the sprue to reduce smears.

[Colorado4wheel]

Keep a damp sponge handy and hold it to the sprue plate about every 4th or 5th time you open the mold.

This will help keep the sprue plate cutting the sprue instead of smearing it.

Ben

I found using two molds solved that issue. I just need to get the molds hotter before I start casting I think.

[Bret4207]

Sounds to me like your mind is made up.

[Wayne Smith]

Something needs to be clarified. Using a one or two cavity mold I have no problem keeping a mole hot when using two. Using a four or six cavity I have to keep focused on one mold. We probably need to mention mold metal here two. I've not tried casting with two brass molds yet - although I can but I think they are all two cavity. Too many variables to make absolute comments.

Colorado is using a four cavity 147gr mold. With that specified I would agree that using more than one mold is probably part of the problem.

[Calamity Jake]

Ben casting using 2 steel molds(single, 2 or 4 cav. 120gr to 300gr in any combination makes no difference) for 30 years, always run the pot temp at 725-750. Always bottom pour, have very few voids/rejects. Now them 37-85gr boolits are another story.

Alum. molds I have trouble with when trying to use 2 molds no matter the number of cavs.
I've tried many different aproaches to using 2 alum molds always with bad results so I use one, set the pot temp at 700, preheat all molds and go to it.

[Colorado4wheel]

Sounds to me like your mind is made up.

Not made up just not taking pat answers of X. I was not having problems for about a year. So I know I can use two molds with out a issue. I think I just need to get them hotter, clean the vent lines and go back to using a off center pour that causes the lead to swirl as it goes in the mold. I am going to try all those first before going to one mold. With one mold I was waiting a pretty long time anyway. I cast pretty fast using two molds. I doubt the time I spend using two molds is any different then the time I spend using one mold and letting the mold cool enough to prevent lead smearing. I think that is why I needed to turn the lead up so high in temp as well.

These are Lyman 4 cavity molds if that still matters to anyone.

[Cap'n Morgan]

I wonder if voids in boolits are the rule, rather than the exception. If the boolit cools too rapid from the outside, shrinkage will "suck" a cavity in the still-molten core. This is a common problem in injection molding of plastic parts with uneven thickness - only here the void often forms on the outside of the part.

Notice this picture from Mann's "The bullets flight from rifle to target". The points of these 7mm bullets have been cut away, and a piece of wire inserted into the exposed cavities:

http://img834.imageshack.us/img834/9140/bulletvoids.jpg

Since the cavities seem to be centered pretty well in the middle, the bullet may not be that much off balance, but it is clearly not an ideal situation.

[Char-Gar]

Colorado..Lots of things work until they don't. A car isn't broken until it is. You have come up with your own notions about how to cast bullets and now it doesn't work for you. Nobody is trying to give you pat answers, just the benefit of experience.

I think you heat sink thingie is a mistake, but do as you wish. One one hand you say you need to cast hotter, but then use a heat sink and two molds. When others suggest you stick with one mold and find a cool the spru on a wet sponge, you think that is a pat answer. Do you see the logical conflict in this?

I don't know how old you are, but there are plenty of us that were probably casting before you were born and have learned a few things along the way. You come here for help and then don't want what you get. Strange..very strange.

[casterofboolits]

I always cast with at least two moulds and sometimes three.

I had a boolit casting business for twenty three years and that is what worked for me to get prduction. I always buy my Lyman four cavity moulds in pairs. Lyman moulds do like to run hot and I normaly run my Lyman four cavity moulds at 750-800 degrees. I pre heat my moulds on the top of my RCBS 10Kilo pots while the lead is getting up to temp and have no problem getting good boolits from the first or second dump.

I have two of the Lyman four cavity 356637 09-147-FPBB moulds. The only problem with them, to me, is that they will not size larger than .356. 9mm sometimes require at least .357, otherwise they can tumble.

As others have suggested, you may be trying to fill the moulds too quickly. Adjust your flow rate to fill slower, but not too slow. Make sure you have a good size sprue without lead running over the sides of the moulds. IMHO voids and poor base fill out are caused by not enough sprue. Also make sure your your Sprue cutter is not screwed down too tight. This will also cause poor base fill out. I have cast and sold several million boolits from Lyman four cavity moulds with out any real problems and they will probably cast as many more.

You just have to learn how to feed lead to these moulds. I just used two four cavity Lyman #358311 38-158-RNPB to cast 1,600 boolits last week.

[Colorado4wheel]

I wonder if voids in boolits are the rule, rather than the exception. If the boolit cools too rapid from the outside, shrinkage will "suck" a cavity in the still-molten core. This is a common problem in injection molding of plastic parts with uneven thickness - only here the void often forms on the outside of the part.

Notice this picture from Mann's "The bullets flight from rifle to target". The points of these 7mm bullets have been cut away, and a piece of wire inserted into the exposed cavities:

http://img834.imageshack.us/img834/9140/bulletvoids.jpg

Since the cavities seem to be centered pretty well in the middle, the bullet may not be that much off balance, but it is clearly not an ideal situation.

Interesting. I am water dropping them so that may make voids more likely?

[Colorado4wheel]

Colorado..Lots of things work until they don't. A car isn't broken until it is. You have come up with your own notions about how to cast bullets and now it doesn't work for you. Nobody is trying to give you pat answers, just the benefit of experience.

I think you heat sink thingie is a mistake, but do as you wish. One one hand you say you need to cast hotter, but then use a heat sink and two molds. When others suggest you stick with one mold and find a cool the spru on a wet sponge, you think that is a pat answer. Do you see the logical conflict in this?

I don't know how old you are, but there are plenty of us that were probably casting before you were born and have learned a few things along the way. You come here for help and then don't want what you get. Strange..very strange.


No, I am listening to the advice as best I can. I am just not ready to give up on casting with two molds. I have to let the sprue cool. While it cools I fill the other mold. Like I said before I am not going to use a heat sink any longer. I am also go to heat the mold more on my hot plate before I start casting. I am also going to be sure and reject more of the first casts. This entire problem may simply be that on a couple sessions of casting I allowed some undersized and poorly filled bullet to go into my bucket. If I stop doing that things might just go back to old normal and I will be happy again. I am just trying to figure out what changed at this point. Not give up on casting with two molds. I am not some kid. I call wheels, wheels not rims (if you even know what that means) and I was around when Datsun existed and I thought Nissan was odd. I am plenty old enough to know when people are trying to help, but that doesn't change the fact that many people told me in the past using two molds can work plenty good enough. I want to keep casting with two molds if at all possible.



I always cast with at least two moulds and sometimes three.

I had a boolit casting business for twenty three years and that is what worked for me to get prduction. I always buy my Lyman four cavity moulds in pairs. Lyman moulds do like to run hot and I normaly run my Lyman four cavity moulds at 750-800 degrees. I pre heat my moulds on the top of my RCBS 10Kilo pots while the lead is getting up to temp and have no problem getting good boolits from the first or second dump.

I have two of the Lyman four cavity 356637 09-147-FPBB moulds. The only problem with them, to me, is that they will not size larger than .356. 9mm sometimes require at least .357, otherwise they can tumble.

As others have suggested, you may be trying to fill the moulds too quickly. Adjust your flow rate to fill slower, but not too slow. Make sure you have a good size sprue without lead running over the sides of the moulds. IMHO voids and poor base fill out are caused by not enough sprue. Also make sure your your Sprue cutter is not screwed down too tight. This will also cause poor base fill out. I have cast and sold several million boolits from Lyman four cavity moulds with out any real problems and they will probably cast as many more.

You just have to learn how to feed lead to these moulds. I just used two four cavity Lyman #358311 38-158-RNPB to cast 1,600 boolits last
week.


Thats has been my experience almost exactly. And I use a .357 die that sizes to just about .356" So yeah, I may have had some poorly filled bullets (smaller) get past me and thats the entire problem with tumbling.

I didn't realize filling to fast could be the problem. I doubt that is my issue but I will experiment and see if that is part of the issue. Thanks.

[williamwaco]

So I filed a bullet in half and sure enough, small void near the middle.



I have wanted to do this for years but never had the motivation to clean up the file afterwards.

The lead totally gums up my files and is a really unpleasant chore to clean them.

How did you manage to file the bullets? Or, How did you clean up the file afterwards?

[Colorado4wheel]

It's just a cheap HF file. I didn't worry about it. I didn't notice a problem with the file while doing it either. I do it all the time to test my bullets with the Lee Hardness Tester.

[KYCaster]

Interesting. I am water dropping them so that may make voids more likely?



No, water quenching doesn't have any effect on voids. If your boolit is going to have a hole in it, it will be there before the mold is opened.

I've often thought that it is very difficult to cast a boolits without voids and impossible to cast them without an internal area with low density.

In order to avoid voids :roll: the cavity has to cool before the sprue so the boolit can suck molten metal from the sprue puddle. If your lead smears when you cut the sprue, that means the boolit is still molten and the sprue is sucking metal from the boolit, resulting in voids.

Regardless of the relative temps of cavity and sprue, the center of the boolit will be the last part to reach room temp, so as the alloy loses heat through the mold blocks to air, the metal will shrink away from the hotter center leaving an area of lower density. If you measure hardness on the base of the boolit, the center will always test softer than the rest of the boolit because of the lower density at the center.

Good casting technique can reduce this effect, but I don't think it can be completely eliminated.

Jerry

[Char-Gar]

I have read for many years about folks using two gang mold to cast a large quanity of bullets in a short time. I have even read some articlex by gunwiters who expoused the same.

Thinking that was the way to go, I have given that a try on several occasion, and found it more of a problem than a help. I ended up with lots of poor quality bullets. When it was all said and done, I got more high quality bullets for the time invested by using just one mold.

Our own Bruce B, taught us how to cool the spru on a damp rag or sponge. When you get the hang of that, production really speeds up. We also learned to put about an inch of clay kitty litter on top the melt to do away with the need for repeated fluxing when we add pre-warmed metal.

All in all, there are better ways to increase production of good quality bullets than using two molds.

I think you are on that same learning curve. But as always read my disclaimer below. Best of luck.

[williamwaco]

I have read for many years about folks using two gang mold to cast a large quanity of bullets in a short time.

I have given that a try on several occasion, and found it more of a problem than a help. I ended up with lots of poor quality bullets.

When it was all said and done, I got more high quality bullets for the time invested by using just one mold.

Best of luck.




One+

Me too.

I can get more good bullets from one two cavity mold than from two identical two cavity molds.

I can get more good bullets from one Lee 6 cylinder than from two H&G four cylinders.

( I AM NOT insinuating that Lee molds are in any way equivalent to H&G molds )

[Colorado4wheel]

I have a temp gauge and I measured the temp of the mold. Basically, the mold was not getting hot enough because I am casting with two molds. I used a hot plate and cast faster. That seems to have solved the issue. Better fill out. Better sizing. More consistent weight. I still need to clean the vent lines but it's far better now. Mold had to be about 50F hotter. I used the bull plate lube and got no smearing. Just a small star shaped divot on the bullets. It was very consistent.

[stubshaft]

Might want to make sure also that you leave a decent dollop of lead on the sprue too.

[Colorado4wheel]

I always leave a good amount of sprue over the bullet.

[Bret4207]

I have a temp gauge and I measured the temp of the mold. Basically, the mold was not getting hot enough because I am casting with two molds. I used a hot plate and cast faster. That seems to have solved the issue. Better fill out. Better sizing. More consistent weight. I still need to clean the vent lines but it's far better now. Mold had to be about 50F hotter. I used the bull plate lube and got no smearing. Just a small star shaped divot on the bullets. It was very consistent.

Really? No kidding? Well golly, I never would have thought of that.[smilie=l:

[Colorado4wheel]

Really? No kidding? Well golly, I never would have thought of that.[smilie=l:

See I was listening. Just didn't solve the problem by giving up on two molds.

[Colorado4wheel]

I have spent some more time with my molds. I have the issue solved. Basically I had some rusty patina inside the molds. I also had some lead in some of the vent lines. I polished the inside of the mold with some bullets and some polish. They are casting great bullets even using two molds at the same time. I know that is disappointing to some.

[canyon-ghost]

But that is the reason to weigh bullets, to find voids caused by air pockets. Good of you to post what you found out. May help to know cleaning the mold helped with that problem. Thanks.

[Colorado4wheel]

Yep, I weighted a bunch of them and found some that were light. On the most recent batch I weighted a batch and they were not light like the others. Interesting enough I think you can feel the light ones go through the sizer. The light ones were also undersized.