Help! 5 cav aluminum mold and cratered bases

[Dimner]

I'm at my wits end. Usually I can get the right pace, mold temp, etc where I can get perfect bases with my aluminum molds. However, this is my first 5 cavity in 30 cal. Before, it had just been 22 cal. That one is easy to regulate mold temp.

The problem I'm having is with cratered bases, ripped bases, pockmarked. Or conversely, when I can produce perfect bases with the mold, I have 85% defects on the body of the bullets due to fillout. I'm pretty sure that's because when I can get the bullets cool enough to cut the sprue without any crater issues, the mold has cooled down too much. Then the next few pours are with body defects.

So when the mold is at proper temp (I think around 425 based on my measurements) and I cut the sprue 3 seconds after the sprue goes frosty, I get constant cratered bases. I have tried the damp cloth on the sprue method of cooling down only the sprue, but either I don't cool it down enough and issues persist, or I cool it down too much and we are back into body defect issues.

I have poured about 5 quarts of these bullets and just cannot find the formula for getting this right. The best I have been able to do is cast 3 cavities at a time with a 40% rejection rate.


Data:
Mold: NOE 30 hunter (311-190-FN) 5 Cavity Aluminum
Alloy: 95/3sb/2sn - pretty sure about this as the components used to create this alloy were assayed.
Temp: Have tried 710 as well as 730 - Using a Hatch made PID
Method: Ladle Pour


First pic, is what I'm expecting as good bases. The next two are what 85% of my casting looks like with this mold.

 

[JustJim]

Try tapping the sprue in the area of problem cavities with a piece of wood. Until the sprue is solidified, you'll get a "flash" of shiny metal. When the area tapped keeps the same appearance, go ahead and cut the sprue. Worked on some of the H&G 8 cavity 30- and 32- caliber moulds I messed with.

 

[JWFilips]

Let them cool longer before cutting the sprues! Even if you have to use a Hickory Stick banger on the Spreu cutter!

 

[popper]

produce perfect bases with the mold, I have 85% defects on the body of the bullets due to fillout

Those really don't look too bad. 5x mould is a problem as one end is correct, other too cold. Had same problem with 6x Lee 30/30, only get 2x now. I had to run about 440 and pour real fast (sometimes get partial pour - maybe what is happening) and then let sprue cool, I use second color change, which is about count of 7. Dump fast for next so the mould doesn't cool too much. GC covers up the crystalized base problem but try to keep it small. I did some PB waiting till the sprue was solid and banged the sprue - got angled bases! Looked real good but created a circle on the target.

 

[Dusty Bannister]

Your temperatures sound about right. Ladle pouring has never been my preference with a multi cavity mold because you often are required to dip one or two more times to completely fill the mold. I prefer to use the Bottom Pour pot so I can fill the cavities much faster and not have quite the temperature fluctuation issues. So my first question is, are you using a stop and fill, stop and fill, stop and fill, at each cavity resulting in a large sprue to make one long connected sprue.

 

[Rick]

I only ladle cast, plenty of alloy for the biggest 6 cavs I have and I pour a lot of alloy. A 2 pound Rowell is your friend. No stopping starting, fill the mold with one sweep across with enough alloy to flow over the side of the mold.

The tear outs your seeing is because the alloy isn't completely frozen yet, just a few more seconds should do it. You'll get an eye for the appearance of the sprue as it freezes.

 

[Ian]

The only time I ladle 6-bangers is with an 18" dutch oven full of lead between my knees and a 2# miniumum Rowel ladle with the handle shortened to about 8". Hold the mould at an angle over the pot starting at the bottom (far) end and get a nice spurt of lead washing back out of the cavity and then top off, move to next and so on. You get really high quality bullets from washing out the bases and then overdosing the sprue. Lead streams off the sprue plate pretty much the whole pour sequence the way I do it.

Those aluminum NOE moulds are a real bitch to break in properly, but once you do (about five long, frustrating casting sessions), they come around and if you haven't destroyed them by then, they will be gems.

A tip I can give you is "Lee-Ment" the mould. All of the vent lines on the right side of each cavity will be completely plugged up with burrs from machining, it pays to open these up by picking them toward the cavity with a sharp scribe under high magnification and then lap them out. Breaking the sharp edge off of the inside top of the blocks also helps the bases vent. Attending to these slight venting problems will enable better fillout at slightly lower mould temperature, allowing you to wait several more seconds for the sprue to set more fully each cycle. There is a sweet spot with ternary alloys where you don't have to beat the plate open with a mallet but neither will you have sprue tears.

Only other thing I can say is I've shot thousands of .30-caliber rifle bullets that all had a uniform "goat ass" crater in the base just like some of yours in the photo and as long as you maintain CONSISTENCY, they will shoot just fine. Don't think the gas check won't flow in there though, because it certainly does!

 

[Bret4207]

What Ian said. You're on the right track but you need to not be at all scared of going what will seem to be overboard on the sprue. It's got to overflow, a bunch. That's putting heat where it needs to be. Then it's just figured the timing to when things are solid enough to cut. They aren't bad bases, really. Toss the worst maybe 5% of them and go shoot.

 

[Dimner]

To add a bit more info....

I have tried bottom pouring, it is pretty much the same. I switched to ladle thinking it would help with the rejection rate.

I fill the cavities in one dip or scoop, I have a big enough ladle for that. One long connected sprue. Dusty, you may be onto something i wonder if i can go back to bottom pouring and try and fill those cavities with individual tiny sprues.... maybe that will allow those sprues to cool faster while maintaining overall mold temp. However, the bottom pour is emptied and put away for the moment, so I'm gonna see about those vents Ian is talking about and try Jim's tapping method.

I do let the lead pour back into the pot as I fill the cavities. As I fill from the front to the back of the mold with an ever so slight angle that let's the lead go back into the pot if I pour too much.

As for waiting for the sprue to harden longer.....
We have 3 stages of sprue
1 - molten (lasts all of 1-2 seconds)
2 - Shiney but solid (lasts about 5-8 seconds on this big mold)
3 - frosted (final state)

I'm waiting till that third state and have tried everything from a 3 to a 10 count after we hit stage 3. If I wait long enough for the sprue to need to be cut with a mallet, I get perfect bases on that drop but the following pour will have body defects on the driving bands (I can show pics if necessary) because now the mold is too cool.

Maybe, I'm thinking I need to show you the body defects on the ones poured after I get perfect bases?

 

[Ian]

If I wait long enough for the sprue to need to be cut with a mallet, I get perfect bases on that drop but the following pour will have body defects on the driving bands (I can show pics if necessary) because now the mold is too cool.

Yep, been there a thousand times. Only good fillout when the mould is absolutely roasting hot, then not enough time for the sprue to set. Try fixing the venting and using a manicurist's fan to knock about two seconds off of the sprue cut time. You want to cut between stage 2 and 3, it lasts about half a second and you have to hit it on the money. Start cutting the instant the flashover starts and by the time the plate is open it's finished.

 

[Dimner]

Popper/Ian/ Bret....

I guess I have been a merciless culler in respect to base defects. So let's talk about what is acceptable. I can take a few pics later tonight on the range of bad to the worst. And Ian I agree consistency is the key here. If I'm gonna settle for cratered sprues, I just needs some guidance here on how to keep them consistent. As I go through bases when inspecting they all look like ink blot tests. What is the criteria for acceptance? Shallow craters? Small craters distributed evenly in the sprue cut circle? One big balloon knot crater?

 

[Ian]

Mr. Target and your personal accuracy standards will be what tells you what is acceptable.

That mould design is a challenge. I the same mould by BRP (original) and two examples of MP's version and they all tend to round out the edges of the bands on either side of the lube groove unless the mould is SUPER hot. inadequate venting is a large part of the issue.

 

[popper]

Yup, mould too cool.

 

[Dimner]

So for tracing the venting lines... what kind of tool could be used for this?

I'm thinking sewing needles? A ballpoint type needle. Or maybe a tapestry needle? Or Should I avoid steel?

 

[L Ross]

I bought a 5 cavity NOE for the XCB bullet. Most contrary mould I ever used. 5 cavities required three different techniques to get good bullets. The good news is that the more I used it the less ornery it got. But, I will never buy a 5 cavity again. I'd be happier with a two cavity. As far as NOE's quality goes, no complaint, 5 identical bullets from the 5 cavities. Beautiful, accurate, bullets with a better ballistic coefficient than my beloved Lee 3120155-2R as demonstrated by less drop over a quarter mile. But the mould itself is a challenge.

 

[Brad]

My NOE moulds either cast wonderfully right off or fight me like Ian mentioned. My first one was a very early NOE, the 165 RD. I hated it for the first few months. Cleaned it, cast, and got poor fill out. Cleaned it again, cast some, same result. Must have the 5th or 6th time I used it that the damn thing settled down and gave good bullets.

I have some others that I didn’t even clean, just got them hot and they gave good bullets pretty quickly.

 

[Dimner]

I bought a 5 cavity NOE for the XCB bullet. Most contrary mould I ever used. 5 cavities required three different techniques to get good bullets. The good news is that the more I used it the less ornery it got. But, I will never buy a 5 cavity again. I'd be happier with a two cavity. As far as NOE's quality goes, no complaint, 5 identical bullets from the 5 cavities. Beautiful, accurate, bullets with a better ballistic coefficient than my beloved Lee 3120155-2R as demonstrated by less drop over a quarter mile. But the mould itself is a challenge.

Don't leave me hanging like that!!

 

[JonB]

Bottom pouring a 5 or 6 cav alum mold:
I pour a lot of alloy for a large sprue puddle, which flows down the sprue plate. I fill the far cavity first, then slide the mold under the pot to fill the next, and so on, filling the closest cavity last. As I do that, I tilt the mold slightly away from me, so the excess alloy flows toward the cavities that are already filled, which keeps them warmer, so when I finish filling all the cavities, the sprues are all freezing at about the same time. Also, I use a small fan blowing into the dump area...this is especially important for large cavity molds.
>>>NOW, I haven't cast any 30 cal bullets for a long time, so I don't recall off hand if I use the fan or not? But if I have a HOT mold and sprues are taking too long to freeze, then I turn on the fan.

As to sprue craters...I don't mind them, but as others said, they need to be consistent. If you have one batch of bullets from the same session, that have varied sprue cuts, sort them out and weigh them...that should tell you something?

 

[JonB]

My NOE moulds either cast wonderfully right off or fight me like Ian mentioned. My first one was a very early NOE, the 165 RD. I hated it for the first few months. Cleaned it, cast, and got poor fill out. Cleaned it again, cast some, same result. Must have the 5th or 6th time I used it that the damn thing settled down and gave good bullets.

I have some others that I didn’t even clean, just got them hot and they gave good bullets pretty quickly.

YES, I whole heartedly agree. Some NOE molds (certain designs I suspect) cast great out of the box...others need several sessions and usually some fiddling as well. I have done what Ian mentioned (Lee-menting) on several molds that gave me troubles, and always got them dropping well.

 

[Dusty Bannister]

As JonB said, and do not skimp on the sprue puddle. By starting at the sprue plate hinge bolt, you are going to have the least stress on the plate since you pour the last one furthest from the bolt so have better leverage. I prefer to stop and fill, then stop and fill, until the last cavity is filled because some sprue holes are a little small as as you move the stream across the sprue hole, it stops proper venting. Do whatever works best for you though. As you can see there are many that prefer one method over the other so use what works for them.