Help: Void issue with new alloy

[BD]

Thanks TurnipEaterDown, (long for Ted?). That is an explanation that I can understand. I am looking for a reasonable place to get my alloy analyzed. In the meantime I will do a short run of .38 158s with the temp bumped up 25 degrees and add a second to the time the mold is left up. Those two things work together as when the temp goes up, the time for the sprue to cool each cycle gets longer or I'll get lead smeared across the top of the blocks. I'll wait to get an analysis on the alloy before I make any changes to it. Although I'll say I'm hoping that something like adding tin to the alloy will be the eventual solution as raising the temps slows the process, and cyclic speed is the whole point of the master caster. When I was younger I could outproduce the master caster using a Lee 6 cavity mold. But at 68 I can't keep up that pace for long. The master caster makes it so easy that I can pull that handle for 2 or three hours continuously.

[fredj338]

It might be the antimony powder. It doesnt alloy well without higher heat. When I need antimony, I buy alloy with it to blend.

[alamogunr]

As it has been recommended, have a sample tested. Look up BNE on this site. He does lead analysis. He also requires that samples submitted be prepared to his instructions and a pound of lead per sample(I think). Requirements for sample prep are not difficult but are not flexible either.

[Willie T]

Considering the only thing you changed is alloy, it is reasonable to surmise alloy as being the catalyst. Adjusting your technique to adapt to the new alloy is part of the deal. I can not see enough detail in the pictures to be certain but It looks like the sprue plate is pulling out a divot rather than making a clean cut on the sporadic bullets with divots in the base. If your new alloy has a marginally lower melt point than what you have previously been casting with, that would make perfect sense. Simple adjustment would be to add a couple seconds longer to dwell time before opening the sprue plate after the mold is up to temp. See if you get nice clean bases with crisp clean sprue cuts with a little more dwell time. The sporadic sprue plug pulling out makes me wonder if you are right at the edge of the bullet and sprue solidifying with the occasional drop not quite having enough cool time when the mold gets a smidge warm. You specify your alloy temperature as being 700°-750°. If you don’t want to slow your production with a slower cadence, it could be that tightening up your alloy temperature range to keep it between 700°-725° might be enough to alleviate the occasional sprue plug pulling out.


Willie

[Castaway]

Check the vent lines on the mould and see if they’re filled in. Is so, judiciously scratch the alloy from the lines. It’s possible the melt is going in and no place for the air to escape, thus the air compresses at the top on the bullet and doesn’t allow for a completely filled mould

[Rapier]

As has been previously mentioned, a change happened, you made a new alloy and you were gone for some time, by your description. If you cleaned your moulds before you began casting again, then OK there. That leaves something is not right with the alloy. That could be two thngs, proper temprature to actually alloy or an inproper ratio of the mix. I would suspect a low temprature in alloying with pure non alloyed metals.

I cast using mulpitle moulds at a time, not the same, however I found that addng antimony and arsnc was best accomplished by adding a previously alloyed metal containing them, at a high temperature. I make my alloy in a 100 pound pot, over a propane burner, it can reach just about any usable heat level. I found that makng a sprue 2x the bullet diameter, with a fast pour gave 100% fill. The sprue must fost over, set, to not pull or smear.

The bullet's accuracy is all about the consistency of the base. If the base is messed up you have paper weight. Just pour them all back into the alloy pot and alloy again. But you need to know what you are working with for sure, to fix it.

[BD]

Sorry I didn't get back to this thread sooner, but in my defense I was under indentured servitude to my daughter for a week remodeling an apartment in a building they bought in southern Maine. ( a common problem among "retired" folk). Before I left I put in a 158 grain .38 mold and started casting while messing with the heat and timing. After the obligatory 50 cycles to insure the mold was up to temp I increased the temp to 775 deg, cast 100, then to 800 degree, while playing with the timing. At 800 deg with an 8 second cycle things started looking better so I cast 20 lbs of the .38 RNFPs. Today I looked through the bin and they all look pretty good. No voids at the sprue. Very nearly what I am used to. The cycle I settled on was 8 seconds: pour, then 5 seconds under the spout before 3 seconds of fans on the sprue then dump. Boolits look good, mold top stayed clean at that timing. No voids at the sprue and clean looking sprue cuts across the board. The only down side, (besides the slower rate),is a very slight finning at the mold joint, a cost of casting at 800 deg. That temp and rate work with this alloy. And I'll probably cast the rest of what I need this season. But then I'm thinking I d better adjust the alloy as the difference between 900 and 1200 boolits/hr is significant.
On the plus side, while I was rooting around under the casting table I found a paint can with about 30 lb of 50/50 roofer's solder scraps. So if it is a tin issue, I'm prepared.
I want to thank TurnipEaterDown, (Ted?) for an answer that clarified things in a logical manner that I could follow. Reminds me a little of the way Felix would respond. I do miss Felix.

[Castaway]

Hate to belabor the point, but if you’re getting finning and lead gets through, so can air and the space between the mould halves is acting like a vent line allowing air to escape. It may not be your problem at all, but your success doesn’t eliminate clogged vent lines

[uscra112]

Something that hasn't been mentioned so I will: Could the thermostat on the pot have drifted? A plausible explanation since you say that increasing the setting seems to have solved the problem. Can you compare with a lead thermometer inserted in the melt?

I've had some similar troubles hand-casting smaller bullets caused by the sprue plate not being hot enough. Charlie Dell mentioned flooding the top of the plate with molten lead as you detach the ladle, and by golly it worked.

[BD]

I do have have more than one thermometer and I keep track of the actual temp in the pot as best I can. And I have been in touch with BNE and will send him a sample as soon as I can get to the post office.

[BD]

This afternoon I lube/sized 500 of the .38s while looking them over carefully. They are better, but the voids are still apparent in 3% of the boolits. The voids are smaller and more uniform, but still occurring. I'll let you know what I find out from BNE.

[Willie T]

If you give your Bullets adequate time to solidify the sprue will quit pulling out. It sounds like you are wanting to cast as fast as you can. If you are not going to slow down enough to let your bullets solidify then you need to lower your pot temperature after your mold comes up to temperature. If you add tin to your alloy it will solidify at a lower temperature than what you are currently experiencing. That means it will require either a longer dwell time in the mold or a lower pot temp to solidify at your current tempo.
Willie

[TurnipEaterDown]

Sorry I didn't get back to this thread sooner, but in my defense I was under indentured servitude to my daughter for a week remodeling an apartment in a building they bought in southern Maine. ( a common problem among "retired" folk). Before I left I put in a 158 grain .38 mold and started casting while messing with the heat and timing. After the obligatory 50 cycles to insure the mold was up to temp I increased the temp to 775 deg, cast 100, then to 800 degree, while playing with the timing. At 800 deg with an 8 second cycle things started looking better so I cast 20 lbs of the .38 RNFPs. Today I looked through the bin and they all look pretty good. No voids at the sprue. Very nearly what I am used to. The cycle I settled on was 8 seconds: pour, then 5 seconds under the spout before 3 seconds of fans on the sprue then dump. Boolits look good, mold top stayed clean at that timing. No voids at the sprue and clean looking sprue cuts across the board. The only down side, (besides the slower rate),is a very slight finning at the mold joint, a cost of casting at 800 deg. That temp and rate work with this alloy. And I'll probably cast the rest of what I need this season. But then I'm thinking I d better adjust the alloy as the difference between 900 and 1200 boolits/hr is significant.
On the plus side, while I was rooting around under the casting table I found a paint can with about 30 lb of 50/50 roofer's solder scraps. So if it is a tin issue, I'm prepared.
I want to thank TurnipEaterDown, (Ted?) for an answer that clarified things in a logical manner that I could follow. Reminds me a little of the way Felix would respond. I do miss Felix.

Glad to be of some help. "TurnipEaterDown" -- deer hunting wise crack.

[BD]

I received the lead analysis from BNE, what a valuable service!
Pb = 95.2%
Sb = 3.3%
Sn = 1.5%

His opinion is that it's a temperature issue. My initial reaction is that I'm a little light on the tin. I'm going to sweeten it up a bit before I cast more.

[Rickf1985]

Always try one thing at a time so that you know what the problem was when it is solved. If you add tin AND heat and the problem is solved that is great but them you will still be chasing it since you don't know which one was the fix. More heat is basically free where more tin is expensive.

[uscra112]

Always try one thing at a time so that you know what the problem was when it is solved. If you add tin AND heat and the problem is solved that is great but them you will still be chasing it since you don't know which one was the fix. More heat is basically free where more tin is expensive.

Can't emphasize this too much. Even though 1.5% does seem pretty lean on tin.