LOTS of Base Voids!!! 124-gr RCBS 9mm Mould/Bottom-Pour. HELP!!!

I've tried turning the heat up to what the SAECO calls 775° F. Bullets are barely frosty, base voids abound, at least 1 out of 4 pours.

I've tried holding the bottom-pour valve open for a full five seconds. Results are TOTALLY inconsistent.

Backed out the stop screw so the stream is consistently a fast-flowing 1/8-inch wide stream. Really changed nothing.

And I'm not talking pinprick holes here. Try a hole as big as the sprue hole, between 1/8- and 3/16-inch deep.

Since the coarse machining marks from RCBS's cherry are clearly visible, and sometimes it even tries to put lead 1/16-inch into the vent lines, I really doubt that more tin or more heat is needed.

But I believe it is most likely related to way-too-frequent failure to fill the full-diameter corners next to the single lube groove. I've scraped that area multiple times with a bamboo skewer but both cavities just don't like to fill out every time.

Wondering if this is a sign of too much heat, or maybe a shrink-happy alloy??? Think what I bought was range lead, it tests out at about BHN 10-11 or so. Need to check that again. With other moulds, I've had great fill-out running hot enough to get light frosting all over, light enough that a lot rubs off leaving "shiny" when handling them during sizing & loading.

Suggestions? I really don't want to pour 150 times to get 50 perfect projectiles!

Large sprue puddle? Pressure fill, then a large sprue puddle?

Might try adding a little tin to your range lead. Also 775* is pretty hot, best results for me have been 700-725 with iron molds.

Sounds like the sprue is hardening before the alloy in the mold cools and shrinks. Might try filling without holding the mold directly to the spout so you can leave a little molten puddle to counter the shrink. I've did this with bottom pour, but it is a little tricky. Fast at the beginning of the pour, the slow at the end. Gotta keep the sprue molten while the bullet is solidifying. I have better luck with a ladle, letting the excess run off the sprue plate and back into the pot.

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Originally Posted by Dusty Bannister

Large sprue puddle? Pressure fill, then a large sprue puddle?

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^^This & don't wait too long to break the sprue open.

How tight is that sprue plate? It should swing open under its own weight. If too tight, you're gonna have issues.

Melt temp is kinda high, back it down to 700-750.

Make sure the molds are clean, vent lines free and mold halves mate together correctly.

With a bottom pour, try to let it run free for a split second every few casts to make sure there is no junk in the bottom.

Any issues with other molds?

You didn't get any sprue lube in the cavity, did you?

another thought: if the lead is pouring in too quickly you can get interesting results. Nice, steady stream is what I use

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I've tried holding the bottom-pour valve open for a full five seconds. Results are TOTALLY inconsistent.

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Your issue is with the bottom pour pot - not the mold. Would guess the end of the spout is NOT firmly fixed into the sprue hole during the pour. The lead being poured into the mold is cooling faster than the sprue puddle
Use a ladle pour casting procedure with the ladle spout stuffed tight in the sprue hole for 5 seconds and at a casting temperature that frosts the sprue puddle at 5 - 10 seconds depending on the bullet weights ... No more casting issue with perfect bullets

Sounds like the OP went to the Goodsteel school of casting. :mrgreen:

Sounds like a mold AND sprue plate temp issue. Lot's said here about mold temp but sprue plate temp is just as important, pour a very generous sprue puddle and don't look at it as pouring lead but rather pouring HEAT.

Rick

VERY RARELY (if ever) do I cast with the furnace spout in contact with the sprue plate.

Instead, I allow the molten alloy a free drop of maybe a half-inch to the sprue plate. I have no trouble with base voids, and a two-cavity mould will usually yield 4-500 good bullets per hour.

If the OP is holding the spout open for five seconds, he is CLEARLY making contact between pot and mould.

Try it without that contact, and the voids should go away.

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Originally Posted by cbrick

Sounds like the OP went to the Goodsteel school of casting. :mrgreen:

Sounds like a mold AND sprue plate temp issue. Lot's said here about mold temp but sprue plate temp is just as important, pour a very generous sprue puddle and don't look at it as pouring lead but rather pouring HEAT.

Rick

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Just what the heck is that supposed to mean?!?!?
LOL!

I recently finished 5000+ 9mm's with a 2 cav Lyman and a PID set at 630° F. I have about a 1/4" drop to the sprue plate. A steady stream and into the hole and not the sprue plate and I get good fillouts every time. Miss either of those 2 things and bases either not filled out or small holes.

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Originally Posted by goodsteel

Just what the heck is that supposed to mean?!?!? LOL!

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Oh,you saw that post huh? Just remembering some photo's I saw a little while ago and the OP's post kinda made me think of them. :mrgreen:

Rick

he is talking about big voids in the base.
this is from rapid cooling, and from the forming boolit not being able to pull more alloy in.

I'd slow the stream down first thing. [this allows better venting and fill out right from the start]
get the heat of the alloy down to about 715-f.
allow the alloy to just run into the mold from the edge of the sprue plate and pour a big sprue puddle.
keep a counting cadence in your head of finishing the pour [counting to 5] then opening the mold.
you'll develop a feel for the cut, try to keep that feeling the same from pour to pour.

I have an RCBS mold that has to have a ladle pour and a 3-5 second pour over the top of the sprue plate and back in the pot for good fill out. I have 4 other RCBS molds that do not. Try that on for size.

Hmmmm....okay. And I was all excited about the mould/bottom pour combo because years ago I cast hundreds of .30 caliber bullets from a single-cavity mould with a similar cone-on-flat sprue plate with nary a problem, using the contact, pour, see a little tiny spash sometimes fly out, and remove with a nice LITTLE sprue to cut off technique. Held contact for only a second or two after I felt/sometimes heard sorta/saw evidence of full fill.

Was even thinking of shopping around for a similar sprue plate for the H&G moulds I've been ladling for years. With those, I really pour heat, starting with a generous tilt, start far away, move up towards myself to the nearest of the four holes, then pour more down the barely-set sprue puddle. Could actually reduce the size of the puddle often, the last of the pour melting a nice channel in the long puddle. Not too fond of having almost as much alloy in sprue as there is in the four boolits.

Next time, and after cleaning up the top of the two-cavity mould's sprue plate, I gotta lube it on top. A bit of lead keeps sticking there. Hard to keep the casting speed up (for mould heat) when it takes 5+ raps on the hinge bolt to get both sprues off.

The sprue plate was badly cupped but fits now. First session after getting it back from RCBS I must not have had enough lube, got some galling circles in the mould around the bolt hole. Everything is stoned down smooth now, and the absence of at least base fins is about the only thing I'm happy about right now.

Guess maybe I need to buy a ladle that has the pour spout/hole. I'm using an open-top right now. Sounds like absent a heating element on/near the pour spout, my technique just won't work even with a bullet that small. On the other hand, I remember it working fine with a 2-cavity .40 mould producing 180-gr bullets...more mass, more heat transfer, hotter sprue, all = lead NOT going solid during my 1-2 second holdopen??? Think the pour hole might be bigger too...

Let's see, a 10-lb pot with about 9 lbs of melt in it + how much 60/40 solder = adding 1% point of tin? Story problems!

Oh, THANKS!!!!! for the replies, information, insights and help. The puddle thing explains why sometimes when one cavity "leaked" at the sprue cone (because of a lead goober/string slipping in there), that cavity was often the one without a void.

Update
Spent so much time cleaning off two moulds last night that I could get in only a few dozen pours. Puddled ones showed no voids but I have not yet weighed them to see if the insides are also good. Think I backed the heat off too much. Based on how quickly the puddle goes solid I think the thermostat needs calibrating.

Cbrick: on further memory searching, I was getting great results and great accuracy out of a .40 2-cavity mould using the contact method. 40% more lead pouring before fillup might have been keeping the bottom pour nozzle enough hotter. I tried pouring more heat to the sprue but just wasn't getting the thing hot enough.

To get a half-inch gravity pour, I would need to elevate the pot to what I consider a dangerous position, 'cause I just can't see to align it otherwise. Stooping to see sux. Or do you guys rig a rest under the pot with some sort of a stop or something to position the mould?

And it's near-impossible for me to either stop one cavity pour to transition to the other hole, AND to try the alternative of moving the mould to continuously pour from one hole to the next. When I try that, a small amount slopa into the second cavity and it tends to harden in a partial boolit before I can get the flow up to speed.

Turn the flow rate down. The lead is going in too fast. Turn the temp up a little hotter than where you are now. Tilt the mold away from you fill the cavity that is farthest from you first do not release the lever and continue to pour into the second cavity. Let it over fill about 1 sec. Then wait count to 8 and cut the sprue. This is how my two cavities work for me. I had a Saeco mold that had to be pressure filled at first. Then I beveled the top edge of the mold and it went away.

try dipping your sprue plate, the section your supposed to hit to open the mold, until the alloy doesn't stick to it.

Then pour your boolits, sounds like your sprue plate is to cold and your alloy is pouring in to fast the combo usually nets you unfilled and rounded base castings.

The above method should give nice clean sharp edges on the boolit base, which is what your after.

Not sure what other molds you've been using but a safe suggestion is No NASCAR casting, slow and steady gets the job done.

You'll also find each mold can require a different technique to get good boolits out of it.

Take your time.