Casting out of round

[Rich22]

Gentlemen

Recently got Miha 9mm grooveless 135gr bb .357 and am having an out of round issue with occassional significant flashing at the bases. Out of round is in the range of 5 to 6 thousandths and has ranged from as low as .353 to high of .363. I am running pot at 725 approx as told via tru tel thermometer. Mold preheated on hotplate to as hot as I can get it and casting as fast as possible averaging about every 15-20 seconds. Mold appears to be closing correctly and I am making sure to not be touching the sprue plate lever only tightly holding the handles. Using bottom pour pot with COWW. Getting good results for fill out when I have everything as hot as I can get it. Essentially what I am finding is if it is not frosted it is a reject. Mold was cleaned with degreaser and stiff brush and brought up to temp and cooled three times prior to usage and I can find no detectable issues but obviously I am doing something wrong. What could I be screwing up here? I have time set aside for the range for load development monday morning so my butt needs to get in gear and get a bunch done correctly here in the next day or so and get them coated with the Hi Tek. Anyone have any ideas I am listening and appreciate all input

Thank you

Rich

[Tatume]

Hi Rich,

Where is the eccentricity? Are the bullets wider opposite the parting line or in line with it? Are all of the bullets eccentric, or just some of them?

If the bullets are larger opposite the parting line, it would appear your mold halves are not coming together. Make sure there is no lead on the faces of your mold that prevent it from closing completely. Squeeze the handles tightly when you close the mold. Check to be sure the alignment pins are not maladjusted, and holding the mold halves apart.

If some bullets are concentric and others are not, then I would suspect your technique. Close the mold and then give the backside of the handle a little tap with a block of wood, to completely close the mold halves (don't beat on it, and don't hit the mold itself).

Another thing to check is lubrication on the alignment pins. They should be lightly lubed with an appropriate grease. I use the little sticks of LBT lube that Veral Smith supplies with his molds. I think it's bullet lube mixed with graphite. Anyway, if the pins are sticking, that will keep the mold halves from closing completely.

Take care, Tom

[Rich22]

Hi Rich,

Where is the eccentricity? Are the bullets wider opposite the parting line or in line with it? Are all of the bullets eccentric, or just some of them?

If the bullets are larger opposite the parting line, it would appear your mold halves are not coming together. Make sure there is no lead on the faces of your mold that prevent it from closing completely. Squeeze the handles tightly when you close the mold. Check to be sure the alignment pins are not maladjusted, and holding the mold halves apart.

If some bullets are concentric and others are not, then I would suspect your technique. Close the mold and then give the backside of the handle a little tap with a block of wood, to completely close the mold halves (don't beat on it, and don't hit the mold itself).

Another thing to check is lubrication on the alignment pins. They should be lightly lubed with an appropriate grease. I use the little sticks of LBT lube that Veral Smith supplies with his molds. I think it's bullet lube mixed with graphite. Anyway, if the pins are sticking, that will keep the mold halves from closing completely.

Take care, Tom


An excellent question, which I will go measure and solve now. Measured 10. all are Eccentric that I measured. Here are 5 of them, 1st number is with the parting line , 2nd is 90 degrees to the parting line. 1 (.361, .355) 2 ( .359 .355) 3 (.358 .353) 4 (.358 .355) 5 (.359 .355). I am attempting to size to .356 so obviously none of these are acceptable.

I checked the mold and found nothing wrong but will do so again. Handles are squeezed as tightly as is possible when casting.

I do use bullplate sprue lube per instructions at the start of all sessions. Forgot to mention that.

I wish I would have checked these prior to casting 800 of these things. I still suspect my technique. I am getting some amount of flashing on the bases of 75% of the bullets, 50% of that is minor 25% moderate and 25% is wow as in a fin that is probably half the bullet diameter.

Appreciate the help

[Tatume]

Hi Rich,

If I'm understanding you correctly, your bullets are wider in the direction opposite the opening and closing of the mold. Although you could possibly shim the mold faces, I don't think a truly satisfactory solution exists. If this is a new mold I would suggest you contact the maker. He may want to replace your mold.

Take care Tom

[243winxb]

Mold preheated on hotplate to as hot as I can get it Warped mould?
The maximum operating temperature should be limited to 400 degrees and the absolute maximum of 450 degrees for a maximum of 30 minutes. At 450 degrees the pins will turn a Pale straw-yellow. Any temperature above this will excessively reduce the tensile strength of the aluminum block by annealing. Once this overheat occurs the only repair possible is replacing the pins and cups with suitable oversize pins.

The aluminum molds will not overheat by simply casting but can be overheated by preheating with a hot plate, torch, setting on top of the pot to heat up or immersing in molten alloy for an excessive amount of time. http://leeprecision.net/support/index.php?/Knowledgebase/Article/View/719/0/alignment-pins-fall-out--overheating-double-cavity-mold

[DLCTEX]

I can't think of any way that a mould could warp that would produce those results over the cavities. The small measurement is indicating the mould is closing too far if that were possible. It sounds as if the mould is cut incorrectly.

[243winxb]

Its been said on here that high heat makes the mold cavities smaller, making smaller diameter bullets. Plus the alloy may be at fault? Seem like you using way to much heat? Try a know good alloy that flows better using less heat?? Casting 800 before checking diameter is a big time mistake. Sorry. Pressure casting (bottom pour spout against mould) will produce more flashing. Try letting alloy drop into the mould.

[upnorthwis]

Before you toss "scrap" boolits back in the pot, you might want to shoot some of them first. Depending on what king of shooting you're doing, they could work just fine.

[williamwaco]

You should not need to squeeze the handles. In some cases that can actually cause the blocks to separate.


Close the blocks, hold the base of the mold up to a strong light and look into the cavities to see if you can see a crack between the blocks.

.

[montana_charlie]

Mold preheated on hotplate to as hot as I can get it and casting as fast as possible averaging about every 15-20 seconds.

Getting good results for fill out when I have everything as hot as I can get it.

I checked the mold and found nothing wrong but will do so again. Handles are squeezed as tightly as is possible when casting.

Preheating the mould 'as hot as possible', casting 'as hot as possible', and squeezing the handles as tight as possible would be enough to make anybody quit casting bullets ... if all of that was necessary.

If you have already annealed the aluminum blocks by excessive preheating, they might be soft enough to make small bullets if you squeeze the handles hard enough.

I don't know how you would check the anneal on the mould blocks, but the maker might deserve a chance to look them over.

CM

[Rich22]

Its been said on here that high heat makes the mold cavities smaller, making smaller diameter bullets. Plus the alloy may be at fault? Seem like you using way to much heat? Try a know good alloy that flows better using less heat?? Casting 800 before checking diameter is a big time mistake. Sorry. Pressure casting (bottom pour spout against mould) will produce more flashing. Try letting alloy drop into the mould.
Using any less heat does not get me anywhere near good fill out and everything is wrinkled. Out of the two sessions or so I can count the non frosted non rejects on 1 hand. This mold apparently needs borderline nuclear kind of heat. According to others on the group buy thread this is normal. Just considering the inconsistencies I was thinking it was my technique. I will give it one more shot tomorrow and see what I can get. Lets assume the mold is good, what can I possibly be doing to cause this? I will agree casting this many before mic'ing the suckers was moronic but at least all I wasted was time and not material.

[Rich22]

You should not need to squeeze the handles. In some cases that can actually cause the blocks to separate.


Close the blocks, hold the base of the mold up to a strong light and look into the cavities to see if you can see a crack between the blocks.

.

Will do that in the morning and report back, appreciate the help.

[Rich22]

Preheating the mould 'as hot as possible', casting 'as hot as possible', and squeezing the handles as tight as possible would be enough to make anybody quit casting bullets ... if all of that was necessary.

If you have already annealed the aluminum blocks by excessive preheating, they might be soft enough to make small bullets if you squeeze the handles hard enough.

I don't know how you would check the anneal on the mould blocks, but the maker might deserve a chance to look them over.

CM

I apologize, I may be exaggerating a bit. What I mean was preheating to approx 350-375 for the mold. Alloy at 725-750 and squeezing firmly, not intentionally trying to crush the thing together.

[Pakprotector]

I'd want to know if you're measuring over the flash and calling that the diameter. I have yet to see this parting line not make a small bulge, but one that goes away if you clock maybe 5 minutes away and measure again. Now if the boolit is football( thinnest 90-degrees from the part, and getting wider approaching the part ) cross section *AND* making lots of flash, I would be much more inclined to question the mold. Again, no need to squeeze hard, just get it closed and pour. IFF you are actually on ragged edge of being too cold, as judged by the fill consider going hotter. Now wrinkles caused by cold v. wrinkles caused by lube migration are similar...:)
cheers,
Douglas

[243winxb]

I would start with my Lee 10 lb pot at maximum temperature and let the alloy heat the mould, till the bullets become frosted. Then drop the pot temp. a hair. If it dont work, return mold. Good Luck.

[HeavyMetal]

I've seen it asked, but saw no response, what alloy are you using?

[JonB_in_Glencoe]

I think it's the mold, Have you contacted Miha ?

[Rich22]

I think it's the mold, Have you contacted Miha ?
I did send a msg via the website, did not get anything back on that but he did respond to another thread. I am going to take everything apart, clean the hell out of it. reassemble, lube. Make sure the handles are tightened exactly correctly and test out 100 or so and see what happens. I really hope I just am screwing something up and that it isnt a problem with the mold. I am fairly inexperienced so that is certainly possible and want to try everything possible before resorting to sending the mold back

[Rich22]

I've seen it asked, but saw no response, what alloy are you using?

Sorry, COWW , Ingots are clean

[mikeym1a]

How many times have you used the mold? I have found that my molds do not cast properly until they have been heat cycled at least 3 times, and then, they still don't cast right for the first 15 throws of the next session. When I pre-heat my molds, I put them on the hot-plate with the sprue plate down, and let it heat the mold through it. The alloy doesn't seem to want to flow if the sprue plate is too cool. I have had a couple out of round molds, but, they were lee's, and got sent back. The eventual replacement was spot on. good luck. mikey

[petroid]

I've had similar issues with aluminum molds using coww. Can you add a little tin to your alloy? It helped me get good fill out without having to cast so hot that the boolits are frosted. It also sounds like your mold is not closing completely sine your diameter is wider at the parting line. I second the idea of cleaning really well and making sure there are no lead deposits on the mold face. The finning is due to the mold not closing completely. Also check your alignment pins to make sure they are adjusted properly. I've had this cause the mold to not close evenly so that the two halves are offset and really messed with the as cast diameters. Hope you figure it out

[Tatume]

Frosted bullets are good bullets. If your bullets are not frosted there's an increased probability of voids.

[petroid]

Tatume, I don't have a problem with frosted boolits as long as they are far enough. In my limited experience and from what others have written, frosting can lead to slightly undersized boolits. Whether this is the issue or not, I'm not sure. But I was just thinking that if the OP's problem was getting good mold fill out, a little tin added to the alloy may help. Pete