six bullet lee mold produces 6 bullets of widely different weights

[emp1953]

the mold is supposed to cast a .357cal 148gr wad cutter. I started weighing them all just as a sanity check. I weighed about 90 and found I had six distinct piles. a low weight of ~141gr, a high weight of 158gr. I had an occasional outlier which I would expect. It looks to me like each cavity produces a unique weight, none of the cavities are the same. This was all with lead that came from the metals dealer with the metal works stamps on it which included 0.999 pure Pb. All were cast from the same pot with no antimony added, and the metal being fluxed periodically. Is it reasonable to expect to get 6 widely differing weights? I have a Lyman 2-cavity mold that gives me 148.3gr from each cavity consistently. Thanks for any opinions.

[gnostic]

Your bullets must have air pockets in them. The few cast bullets that I've checked on a scale were 1/2 a grain or less of each other...

[toallmy]

Can you check the size of the boolits . Possibly touching the third handle opening the mold a little while pouring would explain the difference.

[Dusty Bannister]

A few things that might be causing your problem.
1. Check and verify that the blocks are cleaned and the alignment pins are lubricated and fitted correctly so that the mold blocks fully close and easily open. Heat cycling will help a lot here because the practice helps the alignment pins to settle in position and not shift during use. Shifting pins will either recede into the block and the blocks will slide around, or stand proud and the blocks will be held apart at one end.
2. With the Lee 6 cavity molds, there are the two mold handles and the third sprue cutter handle. Many times a new caster will grip all three together and this actually forces the blocks apart at one end. Do not do that. Close the mold, return the sprue plate to the close position and leave the third handle free.
3. Pure lead? Most will like some antimony and some tin to aid in a well filled cavity. If the melt is cool, the mold is cool, the pour is slow, you are not going to get consistently filled out cavities. I usually set the PID for 720 to 725 and quickly fill each cavity as a single pour per cavity. Fast flow, not slow helps with fill out. If you start the stream at one end and just let it flow til you reach the other end of the mold, you might suffer trapped air in the cavity and size/weight variations will result.

If you still have problems, make sure the mold is up to full operating temperature and cast several cycles and keep the castings in order of the cavities so you can inspect and measure the castings for each individual cavity.

[wwmartin]

The mold cavitys may not all be the same depth. Making the deeper cavity heavier. Check the length of the bullets from each cavity.
Bill

[Castaway]

What DB said. If it keeps up, you might want to mark your cavities and see if the different weights are consistent with the individual cavities

[emp1953]

What DB said. If it keeps up, you might want to mark your cavities and see if the different weights are consistent with the individual cavities

I was going to cast a bunch in each cavity individually (one at a time) to keep them segregated that way, then see if the weights match up to a particular cavity or are random.

[emp1953]

I am careful with the two handle grip. Also careful that the mold faces are tightly closed each time. According to my IR thermometer I am at 725F and the pot maintains that well. Didn't know that the antimony or tin aided in filling out the cavity. Close inspection under magnification shows all the edges and lube grooves to be as crisp as the mold cavities. I have a box of 100 Hornady wad cutters I weighed some. All are within .3 grains of each other, some of that I attribute to the factory lube. I have a flea market hardness tester all it is good for is putting a dent in the lead. With the same amount of pressure on the tester on my castings compared to the Hornady's the dent looks exactly the same depth.

[dimaprok]

You might want to check your scale too. Hard for me to comprehend how you can have 10 grain swing. Even with poor fill out (round corners and wrinkles) I would get maybe 1 - 2 grain max deviation.

[emp1953]

I have both a digital and RCBS balance scale, they are both spot on and read my check weights accurately.

[Dusty Bannister]

Casting a single cavity in a 6 cavity mold is going to introduce the variable due to a cold mold. Pour the full 6 cavities, lay them out in the order of the cavities and lay the next cycle of cast bullets to the side of the previous set. You want to be consistent, and remove as many of the variables as you can. An IR thermometer takes a reading off the surface of the melt and can have accuracy issues. Perhaps someone that has tried them can explain the shortcomings of that tool.

If you have a micrometer, measuring the bullets after cooling can be very informative. Measure across the casting at both sides of the parting line as well as at 90 degrees from the parting line and write those numbers down. They can tell you if there is a mold issue and how much the problem is and if it can be corrected or return with the information to the mold maker for a different mold.

[farmbif]

either the mold is way off or there is some inconsistency in what you might be doing.
is this your first time casting? Are you using a bottom pour pot? or a pan on stove and old spoon or casting ladle? maybe might want to start out with a 2 cavity mold. sometimes things can get a lille wonkey when using larger molds.
I cast some of my best bullets from one and 2 cavity ideal, Lyman and RCBS molds. I know from my own experience even using a 4 cavity brass MP mold takes a bit more concentration and physical agility, and I cast my first bullets more than 40 years ago. And I'm no expert I'm still learning stuff. I have one 6 cavity lee mold I got about half dozen years a go and ive yet to use it.
don't get me wrong, ive got some lee molds but they certainly are not my favorites.

[Jim22]

Your bullets must have air pockets in them. The few cast bullets that I've checked on a scale were 1/2 a grain or less of each other...

Must be light boolits. I regularly see variations of between 1% and 2% of the boolit weight.

[AlHunt]

I'm pretty sure at least one of my Lee 6 cavities does something similar. Not as widely spread as you but definitely some variation. Also when sizing there's a difference in how much force is required to push through. My problem child is a 9mm mold.

[Martin Luber]

I am going to guess that pure lead is not filling the cavities the same. Add 2% tin to improve flow and cast hotter , say 700 to 750 F.

This is likely from a surface cleanliness condition; clean blox with a toothbrush and dawn dw soap.
Degrease with brake parts cleaner and then preheat on low heat on a surface heater element.

Good luck

[abunaitoo]

How do they look????
Round edges????
Lube grooves and base should have sharp edges.
If edges are rounded, it's not filling out.
Could be why the wide weight difference.
Try casting at a higher temp to see if it helps.
I smoke the mold cavities for better fill out.

[myg30]

If all the above fails then Make sure your spruce plate is FLAT from end to end and no day light shinning thru it. Some time you might get a little build up of aluminum around the pivot screw hold when they taped the hole which lifts the end up slightly.
Remove the screw and plate, run a fine flat file across the top of the mold or on sand paper on a hard flat surface with the mold blocks held together. After a pass or two you might see if any high spots.
Lube the pivot screw and install wave washer, snug it up, don’t over tighten.
Also while apart see if the spruce plate is flat and any raised area around the screw hole especially.
Lightly file it flat if needed.

Another ideal all this fails, if your filling mold front to back, try back to front and see if weights change from cavity’s.
Adjust flow and pour faster, and don’t worry about spill over, most time you will have a long solid spruce and not 6 little spruces. Make sure they all change color/ cool before opening.

Clean all the cavity’s with hot soap n water, tooth brush. I warm my molds and spray with brake cleaner. Reheat and cast till wrinkles are gone.

Good luck, I’m sure you will get it working.

Mike

[JonB_in_Glencoe]

A few things that might be causing your problem.
1. Check and verify that the blocks are cleaned and the alignment pins are lubricated and fitted correctly so that the mold blocks fully close and easily open. Heat cycling will help a lot here because the practice helps the alignment pins to settle in position and not shift during use. Shifting pins will either recede into the block and the blocks will slide around, or stand proud and the blocks will be held apart at one end.
2. With the Lee 6 cavity molds, there are the two mold handles and the third sprue cutter handle. Many times a new caster will grip all three together and this actually forces the blocks apart at one end. Do not do that. Close the mold, return the sprue plate to the close position and leave the third handle free.
3. Pure lead? Most will like some antimony and some tin to aid in a well filled cavity. If the melt is cool, the mold is cool, the pour is slow, you are not going to get consistently filled out cavities. I usually set the PID for 720 to 725 and quickly fill each cavity as a single pour per cavity. Fast flow, not slow helps with fill out. If you start the stream at one end and just let it flow til you reach the other end of the mold, you might suffer trapped air in the cavity and size/weight variations will result.

If you still have problems, make sure the mold is up to full operating temperature and cast several cycles and keep the castings in order of the cavities so you can inspect and measure the castings for each individual cavity.

I am careful with the two handle grip. Also careful that the mold faces are tightly closed each time. According to my IR thermometer I am at 725F and the pot maintains that well. Didn't know that the antimony or tin aided in filling out the cavity. Close inspection under magnification shows all the edges and lube grooves to be as crisp as the mold cavities. I have a box of 100 Hornady wad cutters I weighed some. All are within .3 grains of each other, some of that I attribute to the factory lube. I have a flea market hardness tester all it is good for is putting a dent in the lead. With the same amount of pressure on the tester on my castings compared to the Hornady's the dent looks exactly the same depth.

emp1953,
Welcome to the forum.
What Dusty Bannister explained (#2) is the most likely problem for that much weight spread. Lee molds will never be that far off. I hear you say your are careful with two handle grip, but take the extra time to re-examine your technique. when you close the mold with your casting grip, stop and check for a gap.

[sharps4590]

I am suspicious of technique. None of my multiple cavity molds throw that much variance.

[Martin Luber]

Pictures would help too