Mold fractures the meplat on release

[bmortell]

One of my WFN molds a .360 meplat 44 mold makes small fractures on the sides of the nose when released. My theory is the the nose is "too" perfectly flat and square so when the bullets slide out the corner grips and want to pull the edge off.



this is a picture from one recovered from water after it was sorted as good, you can see the mold line bottom center so the sides are the mold sides. some i can see right from The mold that it split but some it forms a fracture but it dont open till it hits something and this worrys me cause a corner could come off in the launch proccess down the barrel and be extremely not accurate at best.

Im assuming id need to make something that reaches in the mold and polishes out the center of the flatpoint to dome it very slightly, but i want feedback before i modify anything.

[JSnover]

Maybe cool the mold a bit before you open it.

[bmortell]

ya I was gonna mention about the cooling time and I could decrease my likelyhood of getting it that way, but I cant always see the crack and sort them out effectively so I could still be getting some that slip through without noticing it.

[country gent]

I would try letting the sprue cool a little more before cutting the sprue also. If this doesn't help then I would try a light polish in the sprue hole to sharpen it a little. Look and see is there is a Straight sided dia under the angled hole. To wide a straight dia can cause this also. I don't think would modify the blocks. It appears to be in the sprue plate itself. A light stoning to sharpen the bottom edge and polish of the sprue hole ( angled potion) will allow the sprue to lift and be cut cleanly. A rough sprue hole holds the sprue in place and it is pushed / plowed off not cut.

[Bloodman14]

We are looking at the nose, right? Is it a nose-pour mold? If so, it is way too hot. If a base-pour mold, still too hot.

[bmortell]

hmm I didn't consider it could happen while im opening the sprue with the mold halves still together, or perhaps they bump apart when I hit the sprue.

[bmortell]

Its a normal base pour 43-300R from accurate molds. But as i mentioned even if i let it cool till i think its solid enough i could still be getting the crack too small to notice by looking at it so that answer dont really satisfy the OCD even through its not happening as much.

[Dusty Bannister]

I think JSnover has given you the best suggestion. If that is a 300 grain bullet, it is holding a lot of heat from the casting. If you are water quenching then you are trying to drop them quickly to get them hard. May I suggest that you try casting at about 725 f, have a slow tempo, but cut the sprue as soon as the puddle hazes over. If the base of the casting appears "wet" it is still fluid. If it tears out the sprue instead of cutting it off, then the casting is still in a slush phase. If the sprue cuts and leaves a nub, then you need to attend to the sprue plate to get a clean cut. Once the sprue has been cut, then allow more time for the casting to become solid. Sometimes with the WFN inverting the mold blocks so the casting wants to fall from the mold, and tapping lightly on the inside of one of the handles will pop the blocks apart and allow the casting to fall free. Several layers of cotton towel padding and limit the height of the fall and see if that produces a better bullet. Dusty

[Walter Laich]

got any more pictures?

that looks awfully rough on the top

mine usually is very smooth

[bmortell]

that's from after hitting water and it expanded 10% wider perhaps which is why its bumpy. but on fresh cast ones its smooth as normal except some have the crack already there that can or cant be seen. I don't have any of those right now for a pic, but the one in the pic did look ok till it hit water and the cracks opened.

[Dan Cash]

Why are you water dropping these bullets, seeking armor penetration? The will work much better if they are much softer.

[bmortell]

recovered from water as in shot at the water that's why its bumpy, I never said I water dropped them from the mold

[MGySgt]

This mold if from accurate Molds??? If so end an e-mail to Tom with the picture and ask him. the nose could be slightly concave that is causing you this problem. Tom can probably figure it out if letting it cool longer doesn't fix the problem.

I have an RCBS 430-250 KT that gives me fractured shoulders if the boolit has not completly solidified when I open the mold.

[bmortell]

ya next batch ill have to cool longer and check em carefully, probably line em up with a magnifying glass. and go from there

[megasupermagnum]

I've never seen cracks, but I know when casting with an alloy high in antimony, too hot bullets can fracture on release. Lower temps, and add some tin.

[Bloodman14]

I re-read the entire thread, but, I am still a bit puzzled; are these fractures happening at the time of release from the mold, or, are we seeing fractures that are occurring after impact with the water?

[bmortell]

any fractures are present as soon as they fall from the mold. I know this because some are visible right off the bat and some are hard no notice but reveal them self after hitting something like water as in the pic but its always the same fracture in the same spot relative to the mold line so it happens from mold release.

[oldblinddog]

You fired that bullet into water? What contained the water? May we see some more (better) pics of the whole bullet, from the side, top, and bottom, please?

[JonB_in_Glencoe]

fractures happen from dropping a boolit that is too hot.
When I'm casting boolits from molds with large cavities, I employ a small fan to create a breeze in the area where I drop the boolits, the mold will cool down between pours if you hold the mold in the breeze. Finding the correct hold time will be a trial and error test.

[winelover]

The other day I was ladle casting with a three cavity NOE truncated cone 9mm mould. I started getting a few with fractured edges on the nose. Was using Rotometals Range Alloy that has a bit of copper in it. I drop my bullets on a pleated/cushioned silicon mat. Disappeared when I let the mould cool a few more seconds, before dropping the castings.

Winelover