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Sort of OT, bullet casting


Oddnews SASS# 24779

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I'm probably going to post this over at the cast bullets forum, too, but I encountered a phenomena Saturday that I've never noticed before.

 

I was casting nominal 230 grain .45 bullets and no, nominal 105 grain .31 bullets for .32-20. The first mold is a Redding-SAECO, the second and older Cramer mold containing two cavities, the 105-grain semiwadcutter (a gascheck design that I use without gas checks), and a spire point of 110 grains that I don't use.

 

The .45 mold likes to be held about an inch or so below the valve of a bottom delivery Lee pot. When it's at operating temps, I throw bullet after bullet with no problem.

 

The .32 mold is another story. My usual technique yields wrinkled, poorly filled-out bullets that cause me to heat the room with all sorts of unfriendly language.

 

While casing over the weekend, in frustration, I tried pressing the .32 mold directly against the nozzle of the bottom-delivery Lee casting furnace. Instantly these "injection molded" projectiles came out perfectly. So the key, at least for that mold, is to press it's sprue plate against the furnace nozzle. I did more than 100 bullets that way without a single failure.

 

Can anyone tell me why this works?

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Several elements of mold design and manufacturing make them cast well at different temperatures and head pressures. Block material, what you are using for a sprue plate lube or a drop-out agent, how well you clean the molds, size of hole in the sprue plate, alloy being cast, venting design of the mold, care with which you keep the venting clean and working as designed, etc. Smaller bullet weights in the same size mold blocks means you put less heat into the mold with each set of smaller bullets you cast. Most folks just note (in a notebook, of all places!) at what metal temperature the mold casts a given alloy well, so they can go back to that temp setting in the future.

 

In general, wrinkling and poor fillout is caused by cold metal, cold mold, or low tin level in the alloy. Easiest to fix is bump the pot (metal) temperature up a little. I find I get a lot of small voids in the bases, and they are not always visible from the base, when I cast with the sprue against the pour valve.

 

Good luck, GJ

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More than likely the mould is too cold. Putting them on the side of the pot generally will not bring them up to temp enough to get good fill-out the first pour, so you are then relying on the casting itself to up the temp. But if they aren't filling out right, they probably aren't falling out of the mould easily either, so it slows down your cadence and the mould never does get up to temp. And smaller bullets impart less heat into the mould anyway, making things worse. I almost always dip the mould into the molten metal. If the mould gets too hot then I just set it aside for a bit or cast slower to bring the temp down. Mould temperature, not metal temerature is the most important thing. I can cast good bullets with a holt mould and lead that is barely melted, but I never get good bullets with a cold mould no matter what the lead temp is. By pressure moulding you are getting the lead into the mould before it has time to cool, plus the extra pressure helps get the lead into all the corners. Pre-heat that mould more and it will probably work fine.

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You can speed up the process of heating the mold at the start of a session by using good mold release stuff. The traditional methods of smoking a mold are OK, but if ya can get hold of Magma "Master Lube" or in a pinch, dry graphite powder or even a #2 pencil to coat the inside of the mold thoroughly before you start. Then you can cycle through the first several pours quickly, cutting sprues JUST after they solidify (as long as the plate doesn't smear) and get the mold up to temp. Otherwise, a small caliber (light weight) bullet will fight you enough that as Slim says, you may not get the mold to temp.

 

I cast a HB 45 bullet with a deep, thin skirt one pro caster said would be "impossible" to cast well as the nose pour design means the lead wants to set before the skirt fills out. That MOULD has to be blistering hot, and I have to actually wait for the sprue plate to cool enough so the sprues set, but not so long that the base pins cool too much. Uing Master Lube or dry graphite, I can cycle the mold several times, making junkers, to get it up to temp, then the mold makes some of the nicest bullets ya ever saw. It's all about getting the mold temp up enough yet not so high the sprue plate smears. Once up to MOLD temp, you might actually be able to back off the pot temp some.....

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If you don't want lead smears thath I suggest you get some Bullplate Sprue lube, available at www.bullshop.gunloads.net AJ, it REALLY works, better than graphite or mould release. I would love to send you a sample as this is one of those things that you just don't know what you are missing if you don't try it. Especially with aluminum moulds.

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The smaller the bullets the more time it takes to heat the mold up to operating temperature. I run my molds between 350 and 400 degrees. To do this I have to speed up the pour cycle to maintain the higher temp.

 

You can get temp sticks from the local welding shop. They look like long crayons. You mark the side of the mold. When the mold reaches the temp the mark melts. If below the temp the mark still looks like a crayon mark. I use both a 350 and 400 to make sure I am running between the two.

 

Cold molds make wrinkles.

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Welcome to the wonderful world of casting pard. Youve just learned one of the arcane "truths" in that every mold has its own preference as to pour rate, lead temp, mold temp etc etc.

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Thanks to all. I've been casting for nearly 30 years (started out casting .45 caliber round balls for muzzleloaders back in my teen years), but these are indeed the smallest bullets I've ever cast, so it's a learning experience.

 

I haven't tried Bullplate yet, but over on the Cast Boolits forum everyone swears by it, so it's on my "to be acquired list." I have had good luck with Midway mould prep (at least in casting .45s, .38s and .458 bullets for .45-70). I haven't "smoked" a mold in the traditional way in years -- vastly preferred the spray mold prep when it became available.

 

Sounds like I need to run both the mold and the alloy at somewhat higher temperatures for success with these little jobbers. Can do on that. For now, I have more than 100 that I know will be within "minute of cowboy" which is all they're required to be (I'm not exactly planning to load these up for deer).

 

Thanks again to all.

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When ya get the mold to spit em out with no delay, you can warm the mold sufficietly for proper registration. I reluctantly admit I don't use a casting thermometer, but my 3/1 WW/Pb alloy in the Master Caster is heated to a dial selection of about 775 degrees. The Master caster won't allow direct head pressure (the liquid alloy drops about an inch to the sprue plate) and the current Barnstormer mold is iron, has a hollow base pin arrangement, and a very thin skirt at the base. I start with the mold "slicked" well to help eliminate any foolishness when trying to free bullets, and cycle the mold as fast as ALL the edges of the sprues frost, indicating they are beyond smearing. It takes several cycles to get up to temp, but ALWAYS my indication is "all edges of sprue frosted" then I crank the handle to open the mold. At some point that is as much as a 12 second delay after the pour, during which time a sufficient amount of the heat of the alloy has transferred to the mold, keeping it HOT. You need that mold HOT enough that all the cavity gets filled, the miniscus of the alloy defeated, any square-ish edges filled, and even fine machine marks on the cavities will transfer.

 

You will NOT see glassy shiny bullets that look like chrome (those will have less than superb registration, and often defects), but instead a very slight frost on the bullets, more an "aluminum wheel" look. Do that on bullets you sell, and folks will call or write to tell you they have not seen that fine registration ever...... Great registration means a faithful bullet that copies the mold-maker's intent every time. They will work for any apropriate application based on shape, load, and caliber.

 

THAT is how we get past "Cowboy Adequate" bullets.

 

(FWIW for main match use, I SHOOT bullets with minor blemishes. I don't sell those, but I know when they are "cowboy adequate" ;) )

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