Questions about Casting Large Boolits

[jethunter]

I'm just started casting 710gr WFN for 500 S&W. I'm getting some small voids in the nose section and I think it's from pouring too slowly. The holes in the sprue cutter limit the speed I can pour.

I'm a fairly experienced caster. Mold is preheated well, pot temp is 850F or a bit higher, fill out on the lube grooves is perfect. Alloy is 4% antimony 2% tin, balance lead.

But there are swirl marks and some small voids in the nose section. I think I need to get alloy into the cavities faster. The bottleneck seems to be the size of the holes in the sprue cutter.

Has anyone else experienced this? Has anyone enlarged the spue cutter holes? I'm thinking of trying that but now that I'm old and smart(?) thought I'd ask here first before I start drilling holes. Thanks in advance.

[rancher1913]

sure sounds more like a cold mold. I do 500 grain ones and to get good fill out and no swirls like you describe, I have to get the mold really hot.

[JonB_in_Glencoe]

Mold is preheated well

there are swirl marks and some small voids in the nose section
My first guess is that your mold isn't preheated well...but that's my guess.
Are your boolits frosted?

my 2¢
I think there is a reason why many boolit casters use a Ladle to cast large boolits. I, myself, have never given ladle casting a good try, but I can say I've cast some large 50 cal pistol boolits (440gr and 550gr) and casting large boolits with a bottom pour pot is something I've found challenging. The mold needs to be preheated enough, but then the mold is easily overheated when pouring that much alloy into a mold. It takes practice to develop a slow rhythm, adding a small fan to blow on the mold during casting can help.
Hope those few tips help.
Good Luck.

[jethunter]

I cast quite a lot of 500gr and 535gr for 45-70, and some .600" 530gr for Martinin Henry and haven't seen this issue before. The sprue is taking about 35 seconds to cool sufficiently with a fan which I think indicates a good mold temperature for a bullet this large, and pot temp is approaching 900F. In the past I've been able to solve these problems by going a higher temperature but not this time.

Bullets aren't frosted or overly shiny, they look about right for this alloy.

Has anyone enlarged sprue cutter holes for large volume bullets?

[Tom W.]

Never did any that heavy, but did make quite a few for a .480. The mold has to be good and hot, but you know that. I used to strive for frosted boolits, when they started to take a longer time to solidify I'd turn the heat down just a little and continue on.....

[Grmps]

If you are bottom pouring, hold the mold against the spout and see if that help.

What mold manufacture is it? does it have adequate venting inside the mold?
Sometimes you can use a fine diamond hone or sharpening stone and lightly east the top corners of the mold under the sprue plate to help with venting.

As with any mold problem, the first thing I do is clean it again thoroughly, just in case I missed something the first time.

The only time I have had to cast over 750° is casting buckshot in Lees 18 cavity mold.

[JonB_in_Glencoe]

when you cast for for 45-70 and Martinin Henry, are you using that same alloy?

[jethunter]

when you cast for for 45-70 and Martinin Henry, are you using that same alloy?

yes for 500gr 45-70. Softer for the MH and Postell bullets.

[jethunter]

If you are bottom pouring, hold the mold against the spout and see if that help.

What mold manufacture is it? does it have adequate venting inside the mold?
Sometimes you can use a fine diamond hone or sharpening stone and lightly east the top corners of the mold under the sprue plate to help with venting.

As with any mold problem, the first thing I do is clean it again thoroughly, just in case I missed something the first time.

The only time I have had to cast over 750° is casting buckshot in Lees 18 cavity mold.

Ladling. Accurate mold 3-cav. Cleaned well - scrubbed in boiling water and dish soap, rinsed in clean boiling water, and preheated well. I am fairly experienced, I cast about 50,000 bullets a year and sell them.

I've heard of some casters having a similar problem and needing to enlarge the nozzle on the ladle to get a faster pour in large volume bullets.

Poor mold venting could be the issue all right. I'll give it another scrub and use a hardened scribe to softly clean the vent lines.

[cwtebay]

I'm just started casting 710gr WFN for 500 S&W. I'm getting some small voids in the nose section and I think it's from pouring too slowly. The holes in the sprue cutter limit the speed I can pour.

I'm a fairly experienced caster. Mold is preheated well, pot temp is 850F or a bit higher, fill out on the lube grooves is perfect. Alloy is 4% antimony 2% tin, balance lead.

But there are swirl marks and some small voids in the nose section. I think I need to get alloy into the cavities faster. The bottleneck seems to be the size of the holes in the sprue cutter.

Has anyone else experienced this? Has anyone enlarged the spue cutter holes? I'm thinking of trying that but now that I'm old and smart(?) thought I'd ask here first before I start drilling holes. Thanks in advance.I'm certain that you are getting very sage advice from these other fellas, but thought I would add that I had the same issue casting for a 500/465. I would get absolutely beautiful bullets, sharp grooves, clean edges - until you looked at the nose. Swirls on nearly every one, cross sectioning revealed cavities. Someone else from this forum recommended that I immerse my mold base in my pot while pouring. Voila'!! Perfection. The mold was far more massive than any others I had used before and was not heating uniformly. Also, using a torch cleaning file, and making sure your ladle spout is large enough also helped.
Good luck!

Sent from my HTC6545LVW using Tapatalk

[MOA]

The big downside to enlarged sprue holes is when you go to cut it the greater amount of lead now created by the enlargement will be harder and more force needed. I had to open up two Lee .515 molds and now can only cut the sprue with a protected headed hammer.

[44Blam]

What I found with bigger boolits is that you cast a few in quick fashion and toss 'em back to heat up the mold (in addition to the hot plate).
That heats the innerds of the mold. Then you quickly pour lead into each cavity. And then you whistle a little while you watch the sprue cool and then give a little while to let it kind of gel in the mold.
What I found is that the bigger the boolit, the slower the process. I've got some 80 grn 30s that you have to cast fast to keep a good fill out. Then I've got a mold the makes 240 grn .430s that you slow down for. Then my 400 grn HP mold for my 45 is even slower. It just takes time to heat up the mold and also takes time to cool it down...

[Grmps]

This may be a dumb idea but, try tilting the mold when you start pouring, see if that improves the fill at the tip. I know with the bottom pour sometime where/how the flow of the lead enters the sprue hole makes a difference.

If you decide to enlarge the sprue hole, don't do it on the mold and make sure you smooth/polish the bottom well.

[jethunter]

The big downside to enlarged sprue holes is when you go to cut it the greater amount of lead now created by the enlargement will be harder and more force needed. I had to open up two Lee .515 molds and now can only cut the sprue with a protected headed hammer.

Good point and makes sense. I didn't consider that.

[Dieselhorses]

Mine did the same with 440 gr for the 500. Once mold got hot enough, no more veins and filled wonderfully.

[jethunter]

This may be a dumb idea but, try tilting the mold when you start pouring, see if that improves the fill at the tip. I know with the bottom pour sometime where/how the flow of the lead enters the sprue hole makes a difference.

If you decide to enlarge the sprue hole, don't do it on the mold and make sure you smooth/polish the bottom well.


Mine did the same with 440 gr for the 500. Once mold got hot enough, no more veins and filled wonderfully.


What I found with bigger boolits is that you cast a few in quick fashion and toss 'em back to heat up the mold (in addition to the hot plate).
That heats the innerds of the mold. Then you quickly pour lead into each cavity. And then you whistle a little while you watch the sprue cool and then give a little while to let it kind of gel in the mold.
What I found is that the bigger the boolit, the slower the process. I've got some 80 grn 30s that you have to cast fast to keep a good fill out. Then I've got a mold the makes 240 grn .430s that you slow down for. Then my 400 grn HP mold for my 45 is even slower. It just takes time to heat up the mold and also takes time to cool it down...

Good points, mirror my experience when I started casting 535 postell and 500 gr WFN 45-70 bullets. I'm getting good fill with sharp edges on the grooves in the 700gr bullets. The swirl marks don't bother me, they tend to fade away when the bullet ages a bit but there are some small voids if you look closely and that's what I'm fighting against right now. I've cleaned the mold again and will try it tomorrow . Won't enlarge the sprue cutter holes just yet.

[Michael J. Spangler]

Can you post a picture of the cavity?
I’m wondering if there is just very little mass to the mold near the nose end of the block. A thin wall here could cause rapid cooling and give you fits.

[ABJ]

I have cast a lot of large boolits in both pure lead and alloy's. Ladle casting is tough on long boolits. I drilled the spout of an RCBS ladle to allow the lead more head pressure and volume out of the ladle. Pressure casting also worked good. The best way I have found is, I got one of the new Lyman bottom pour and get the mold real close to the spout and open up the flow control. Head pressure and speed/volume going into mold seems to work the best for me. Like was said before, make sure the mold is venting. If I had to do it with the ladle I would pressure cast.
Tony

[jethunter]

Can you post a picture of the cavity?
I’m wondering if there is just very little mass to the mold near the nose end of the block. A thin wall here could cause rapid cooling and give you fits.

I think you have something there, the cavity wall between the end of the nose and the outside of the mold is very thin.


I have cast a lot of large boolits in both pure lead and alloy's. Ladle casting is tough on long boolits. I drilled the spout of an RCBS ladle to allow the lead more head pressure and volume out of the ladle. Pressure casting also worked good. The best way I have found is, I got one of the new Lyman bottom pour and get the mold real close to the spout and open up the flow control. Head pressure and speed/volume going into mold seems to work the best for me. Like was said before, make sure the mold is venting. If I had to do it with the ladle I would pressure cast.
Tony

I cleaned the mold again and it was venting better today, also raised pot temp up to 900F. Still some bullets with small voids but most were good. I think I can improve my pouring technique and get 100%.

Thanks to everyone.

[JSnover]

A friend of mine lightly taps the mold (500gr 45-70) as soon as the puddle forms on the sprue plate, claims it knocks out any bubbles in cavity. I have no idea if this is a common practice or if it even works. When I cast that size I don't get enough of a weight variation to make me think I have any air trapped in the boolits.

[GregLaROCHE]

I cast quite a lot of 500gr and 535gr for 45-70, and some .600" 530gr for Martinin Henry and haven't seen this issue before. The sprue is taking about 35 seconds to cool sufficiently with a fan which I think indicates a good mold temperature for a bullet this large, and pot temp is approaching 900F. In the past I've been able to solve these problems by going a higher temperature but not this time.

Bullets aren't frosted or overly shiny, they look about right for this alloy.

Has anyone enlarged sprue cutter holes for large volume bullets?

I cast .45-70 500grains in a Lee mold. I know I get best results when lead and mould are hot. Just below frosting temperature. The mould gets too hot fast, so I cool it down on some wet rags or sponge often during casting.

I was wondering about the time it takes for the sprue to cool? For me its 3 to 5 seconds when things are going well. Was your 35 seconds a typo or does it really take that long to cool? If so, I think your mold has gotten way too hot.

[country gent]

One thing to offer here, If you decide to open the sprue holes up. Remove sprue plate from mould and set up flat in a vise. Lock down to drill press table centered. Find a pin pin 4" long that just fits in the chucks key hole. use a counter sink to cut the hole bigger. To avoid chatter and grabbing lower spindle into hole and turn by hand using the pin for a handle. Most drill press run to fast for heavy countersink operations. Using a bigger drill and opening the hole up leaves a web or flat on the sprue hole where it cuts making it harder to cut the sprue since your driving the flat and not a sharp edge. When the hole is opened up lay plate flat on a flat surface and sand paper and remove burr and any displaced metal

[Michael J. Spangler]

I think you have something there, the cavity wall between the end of the nose and the outside of the mold is very thin.



I cleaned the mold again and it was venting better today, also raised pot temp up to 900F. Still some bullets with small voids but most were good. I think I can improve my pouring technique and get 100%.

Thanks to everyone.


You could probably test it by keeping your alloy temp lower where you normally cast your heavy bullets then just rest the mould on a warm hot plate between pours. Keep that section warmer.
I guess an armed thermometer could tell you how much temp you’re losing at that thin section too. It’s acting like the fins on a heat sink.

[robg]

Run big molds hot and fast to get good fillout .opposite when using normal molds then I use 2or 3 molds at once to allow them to cool down before dropping boolits.

[jethunter]

One thing to offer here, If you decide to open the sprue holes up. Remove sprue plate from mould and set up flat in a vise. Lock down to drill press table centered. Find a pin pin 4" long that just fits in the chucks key hole. use a counter sink to cut the hole bigger. To avoid chatter and grabbing lower spindle into hole and turn by hand using the pin for a handle. Most drill press run to fast for heavy countersink operations. Using a bigger drill and opening the hole up leaves a web or flat on the sprue hole where it cuts making it harder to cut the sprue since your driving the flat and not a sharp edge. When the hole is opened up lay plate flat on a flat surface and sand paper and remove burr and any displaced metal

Makes sense. Good points, thanks.

[jethunter]

I cast .45-70 500grains in a Lee mold. I know I get best results when lead and mould are hot. Just below frosting temperature. The mould gets too hot fast, so I cool it down on some wet rags or sponge often during casting.

I was wondering about the time it takes for the sprue to cool? For me its 3 to 5 seconds when things are going well. Was your 35 seconds a typo or does it really take that long to cool? If so, I think your mold has gotten way too hot.

Is your Lee Mold a single cavity? They cool much faster than multi cavity molds.

35 seconds is correct, for big bullets I've always needed to run high temps to get good fill-out and adjusted the cooling period accordingly. Bullets are not frosted.

[Bird]

Sounds like you are losing too much heat through the base of the mold. Keep it in the lead pot before pouring, and drop the pot temp back down to 725 deg or so.

[country gent]

Keeping the mould up to temp may be an issue if it is a thin section under the nose as has been said. I have seen sprue plates pull heat from the stream and cause issues. on a bottom piur pot this is harder to do but you might try over filling the sprue hole to almost cover the whole plate to keep everything up to temp. Check vent lines and clear carefully.

I cast 550 grn 45s in brass mould with no issues but I ladle cast and don't pour a sprue but pour the whole ladle of lead into the cavity letting the excess run off and back into the pot.

At 710 grns its going to empty a pot quick so dipping may work for a short time. An aluminum mould losses heat quickly and a thin section may act like fins on a air cooled cylinder. Steel moulds are better for holding temps and are heavier. Brass blocks heat evenly hold heat longer but can be a very heavy set of blocks. My brass moulds take almost twice as long to cool as the steel do at the nd of a session.

[rrob692326]

I cast some pretty big boolits for my .585 Hubel. 780 grain and 1150 grain and found that if I run the mold hot I have no problems with fill out or voids. My molds are mehanite for these and the biggest aluminum I have is only 500 grains but gives no such problems.

[Motor]

I actually increased the holes in my spure plate (Lee 440gr) for the same reason. Lee has made these with so little metal that it's virtually impossible to keep this mould at a "good" casting temp. I simply run it hot and accept the frosted ones. I powder coat them anyway. :)

Motor

[Dieselhorses]

900 degrees? My pot barely reaches 750 degrees and as long as my mold is heated properly I have no issues. That melt has to pour quickly to retain temperature until filled out. Of course I'm only pouring 440 grain bullets in a 2 cavity mold. How many cavities is yours?

[jethunter]

900 degrees? My pot barely reaches 750 degrees and as long as my mold is heated properly I have no issues. That melt has to pour quickly to retain temperature until filled out. Of course I'm only pouring 440 grain bullets in a 2 cavity mold. How many cavities is yours?

3 cavity