mold is suddenly finning

[jeff100]

I have a Lee 6 CAV 358-158-RF bullet mold that I've had for several years now that is suddenly casting bullets with fins mostly on the nose. I'm at my wits end with this problem. I've inspected this mold using magnification looking for lead or minute specks of lead, the mold seems to be very clean. I've checked the blocks for warping, don't find any warping. I changed mold handles, I've changed how I hold the mold while I'm pouring lead, careful to avoid the sprue cam lever while pouring lead. Nothing seems to matter, the mold is still, sporadically casting bullets with fins. I've cast single bullets to isolate which bullet cavity is the culprit, but the finning problem migrates after I identify one or two cavities as being the 'problem' cavity. Before I junk this thing, what am I missing? Oh, I also clamped the blocks together in a heavy vise with as much pressure as I could leverage for 24 hours to see if that would help. It didn't. Open to suggestion. This is really puzzling. This mold has in the past worked well, casting very nice bullets. Initially I did find lead in the mold preventing the mold blocks from closing properly. That's what started the problem. That lead contamination on the mold blocks is long gone, but the problem remains. Don't know what else to do, what else to check...JJ

[jeepguy242]

There is either a price of Lead you are missing or the mold got too hot and warped.

Check in the alignment pin holes and around the pins.

Have you dropped the mold recently?

[jeff100]

Have you dropped the mold recently?

No, never. That said, I did carefully hone one of the corners of the mold that looked like it might have got banged a bit. Took a file to the face at that corner, but didn't seem to remove little, if any material. Nor can I see any light in the bullet cavities with the mold blocks lightly clamped together. JJ

[country gent]

Check pin alighnment. Check in the pin holes carefully for lead or crud build up making pins sticky or bind. Also run a q-tip around edges of cavity and blocks, pulled fibers will show burrs that may have came up. Set the block with female holes on a piece of glass and look for areas not touching. A good straight edge ( 6' steel ruler) may also show the low spots.

[kungfustyle]

Are the boolits out of round? If so, then something is holding them open pins, handles off, lead stuck somewhere. Try to set the mold on a flat surface to close when casting see if that helps. What temp are you casting? If over 750 back it off. Try to cool the mold down about every third cast with a wet towel on the side Try to ladle pour, if top poring or don't pressure pour. Good luck to you.

[Dusty Bannister]

Suspecting there is contact that you are not seeing, remove the blocks from the handles. Smoke the mate surface of both blocks with a butane lighter. Swing the sprue plate out of the way. Put the blocks together in the correct casting position with the sprue plate out of the way. First see if the blocks tend to "teeter" when pressure is applied to the top of the mold half and then the bottom of the mold half. That would indicate an obstruction that you need to find. Slide the two blocks in opposite directions a couple of times. Then try to rotate the blocks in opposite directions. Pull the blocks apart and inspect for any spot where the smoke has worn away and you will have found the high spot. If you do have block movement while doing this, then the pins might have moved and you need to look further. I have to wonder what you were trying to fix by smashing the blocks in a vise without knowing there was a need to do that. These are soft aluminum blocks and can distort under that kind of pressure. Let us know what you find from this procedure.

[texassako]

I have one that the sprue plate cam likes to try and hold open a bit if I don't watch out. Check to make sure you are not putting any pressure on that sprue plate handle and that the blocks stay closed when the sprue plate is closed.

[runfiverun]

also check for wear where the sprue handle goes against the mold it might be 'over camming' and pushing the blocks apart when closed.

[Walter Laich]

I have one that the sprue plate cam likes to try and hold open a bit if I don't watch out. Check to make sure you are not putting any pressure on that sprue plate handle and that the blocks stay closed when the sprue plate is closed.

second this
when holding the mold closed for the pour use just the two handle that are on the mold. If you put any pressure on the sprue plate handle it will open the mold and you will get finning.

also had a lee that had an alignment pin come loose and keep the mold open

[mozeppa]

here is a question no one has asked...

have you used a dremil to polish the mold halves?

[jeff100]

here is a question no one has asked...

have you used a dremil to polish the mold halves?

No, what would I polish?

[Grmps]

Would you post some close-up pictures of the mold halves

Also, check the leading edge of the sprue plate where is fits around the stop pin for any burs that might be keeping it from closing properly.

Occasionally I will gently tap the handle (with a small leather mallet) where it contacts the mold with the mold fully closed to assure complete seating of the alignment pins/closing

[OS OK]

Melt and Mould together got too hot.

You say you can't see daylight when they are closed with a firm grip on the handles...not touching the sprue handle?

This is my story and I'm sticking to it...
Melt and Mould together got too hot.

Been there...done that!

[swheeler]

I'm guessing you have a loose alignment pin since you say it migrates from cavity to cavity, guess could be handles interfering with blocks also? I sure wouldn't clamp them in a vise and reef on it though, just doesn't sound right.

[runfiverun]

I dunno I have had some LEE molds in the past that putting them in a vice and hammering them into shape sure made me feel better about things.

[Forrest r]

I dunno I have had some LEE molds in the past that putting them in a vice and hammering them into shape sure made me feel better about things.

+1^^^^^

Had the same lee 6-cavity mold start to do the same thing the op pictured above. Got the mold extremely hot and put it in a vise and and tightened the vise up tight leaving the mold to cool. Doing so ended the finning. Used that mold for a couple years after that and ended up giving it away to a friend that bought a lever action rifle chambered in 357.

[6bg6ga]

The only thing that can be happening is either you have some lead attached to the mold, lead in a alignment pin hole or the mold is warped all to heck.

This is why I don't buy and or use aluminum molds or sorry Lee molds.

[buggybuilder]

I had the same problem with a .32-40 mold. I was using the LEE drip can for years and never had a problem...suddenly fins. I did the mold clean-up ritual and nothing helped. Started using the ladle and I have not had a problem since. I don't know what caused the problem but it's solved now.

[mozeppa]

No, what would I polish?

sometimes people will polish the cavities with a dremil in hopes of getting better release on molded boolits when they stick in the mold halves....so they polish.

and when the buffing point spins near the edges where the 2 halves come together a tiny bit of metal can easily be
buffed away ...now you have finning.

[Texas by God]

I have one Lee mold that will fin unless I invert it and smack it with a wooden dowel every so often. I can't find any lead stuck anywhere and it drops great boolits so I don't care.

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