New problem

[Cherokee]

I've got a Lee 356120TC 6 cv mold that I have cast thousands of bullets with without any problems until today. The 6th cavity (at the hinge) is producing a bullet with a dent in the side just above the base. I have carefully examined the mold and can see nothing wrong - that cavity looks just like the other 5. I can't think of anything that is different in the process. Opinions from the group ? This one was a poor cast but is typical of the new problem.

 

[Brad]

Is the bullet hitting the blocks when dropping? I have that issue with some Lee 6 cav on the hinge end. The blocks don't open real wide on the hinge end and the bullets can easily strike the block.

 

[Cherokee]

I was very careful several times in opening and dropping the bullet from that cavity, even casting only from that cavity, so I don't see that happening.

 

[Brad]

Wow, that is beyond a dent. Almost certain something is on the block, right on the bevel base. That is significant. Can you get good photos of the blocks? Photos seem to magnify every little flaw.

 

[Cherokee]

There is nothing I can see on the blocks that is different from the other 5 cavities but I'll get some more pics and post them later...got to go for now.

 

[bosterr]

There is nothing I can see on the blocks that is different from the other 5 cavities but I'll get some more pics and post them later...got to go for now.

 

[bosterr]

Poor venting in that cavity only?

 

[Chris]

I'm curious. Is the dent always in the same position i.e 7 o'clock?

Hav not seen this problem before.

 

[Rick]

Not the best picture to make a judgement call from but it has the appearance of too hot alloy and too cool blocks. The blocks trying to draw heat from the not yet frozen bullet. See the liquid alloy dripping from the hole in the lube groove? The blocks caused the alloy to freeze near the blocks yet the center of the bullet is still liquid. The nose of the bullet had semi frozen allot torn away when the bullet dropped from the blocks. Again not the best picture but it appears the pot temp is too high and the blocks too cool.

 

[RBHarter]

That looks like some sprue lube in the cavity .
I get that occasionally when I re-wet a hinge point or get over zealous with the plate face lube . The nose looks like it has lube craters also.

 

[Chris]

I think Rick and RB might be onto it. Also notice a pinhole with rounded edges to the right inside the lube groove. How about scrub with hot water and soap, then preheat the blocks and give it some hot alloy?

 

[Cherokee]

Here are some better pictures of the bullets but the depression is not so clear

These are poorly cast solely for the purpose of posting this problem. When casting earlier, all the bullets from the 6 cavities were great, but the 6th cavity had
this dent. The dent is always in the same spot. You can see this is right at the edge of one half of the cavity. I thought of a venting problem but can see no
reason. I have scrubbed the offending cavity with a bamboo stick to get anything out that might be stuck but I neither saw anything nor saw any difference
after "sticking" the cavity - the above pics are of bullets quickly cast afterwards. Thanks for the comments, I'll give it another go tomorrow.

 

[Brad]

Weird. Very consistent in location and shape.

 

[Dusty Bannister]

I would consider it likely that you have a lube issue in the mold cavity. I am also seeing where it appears that the bullets are landing on other bullets. Is there plenty of room on the towel or are they striking other previously cast bullets. I would also watch for one end of the mold blocks sticking and then coming loose which allows the other end to pivot and strike the cavity of a yet to release bullet. If the blocks are a little loose on the handles there can be a lot of wobble. Maybe the mounting screw is a little loose or the hole in the handles are worn. I usually run a little on the hot side, and your alloy or blocks look a little on the cool side because they are shinny and not slightly frosty.

Is that a crack in the lube groove, or just a reflection?

 

[Brad]

Looks like a wrinkle in the groove. He did say they were cast poorly just to show the flaw. I think that means he didn't work to get the mould up to temp and that would explain the wrinkle. The flaw is quite clear.

 

[fiver]

it's like there is a void right there.
almost like the alloy is sucking air in that part of the mold instead of lead from the sprue.

I'm curios to see what the inside of the bullet looks like right there.

 

[Dusty Bannister]

Yes, he did say the mold was probably not up to temp, but that crack or wrinkle is in the same location as the void in the original picture. Perhaps the flaw is related? I have seen castings fracture when the bullet did not release freely from the mold which could also be part of the problem here as well. We are still just asking questions to better understand what might be going on to cause the problem.

 

[fiver]

are you pouring this cavity first or last?

it's like the lead supply is freezing while the bullet is sucking on it and it's getting air instead from where it was pushing it out.

 

[Cherokee]

Thank you for your comments. The 6th cavity is normally the last one cast but I try to maintain a liquid state and it is the last cavity to freeze. The samples pictured were poured separately. The mold is pre-heated and the alloy at ~725* on the RCBS pot. That combo works great usually and has with this mold for years, this just started happening. I cleaned the cavity and wiped down everything, made sure there were no lead particles stuck anywhere. Pot is warming now and I'll give it another go.

 

[Dusty Bannister]

Would it be helpful to know what you used to clean the mold? The earlier photos suggest the presence of oil residue. Are you using brake cleaner or some other petroleum solvent? Pre-warming on the edge of the pot, or on a hot plate, and are the blocks open for air movement or closed? And, what is the ambient air temp. A lot of folks are now casting in unheated areas and that has resulted in significantly different conditions and mold performance.