my first brass mold, help me use it!

[Seth_AZ]

Hi all,
A couple of weeks ago I PMed Mihec when it came out that he still had some of the 4-cavity 148gr HBWC brass molds in .38 caliber from a former group buy. Well, it arrived today.

It looks absolutely fantastic. It's my first-ever brass mold, and only my second custom mold (first was a 4-cavity LBT in .40 caliber). I've never used a brass mold before, and I've never used a mold with pins for casting hollow points. Also, frankly, I've never used a mold lubricant like the sample that came with this mold.

Can anyone give me some guidance on things I need to watch out for with this mold so that I take good care of it and avoid accidentally harming it? For instance, in the past I've dabbed a bit of bullet lubricant on the sprue plate screw and mold alignment pins and called it good, hoping against hope I wouldn't put too much on and have it get into the cavities. How does one use this type of lubricant that came with this mold?

I've read that it's possible to solder a brass mold together. What do I need to know about this in order to avoid it?

I've watched a video on Youtube with a guy showing how he casts with this type of mold with the hollow-base or hollow-point pins. I think I'll have that figured out in short order. Any advice or helpful commentary will be read and digested gratefully, however.

[geargnasher]

Rule #1, don't put boolit lube on it, anywhere. Go to either the boolit lube forum or the mould forum (I forget which) and read the "sticky" thread on how, when, and where to lubricate a mould with the light oil.

Brass moulds like lots of heat, like a good pre-soak in a "mould oven" which is any sort of sheet metal box on top of a hotplate before you ever start casting, then run them very fast to keep the pins hot so the boolits don't stick and the bases fill completely. Overheating our alloy won't do it, it's the fast casting to get the mould hot that makes good boolits. If you're running wheel weight metal, then 725F ought to be plenty, if going softer in a relatively tin-free alloy, you can go above 750, but not too much or you'll create some additional problems.

High-tin alloys, especially OVER-tinned alloys (ones that contain more tin than antimony, or close, or some of the type metals) are usually the culprits with "tinning" the mould. Never heard of sticking one together, but I suppose anything is possible. Your best bet is to first clean the mould really well with hot, soapy water and a toothbrush, especially the cavities, rinse well, make a mould oven and heat the mould up to about 400F and slowly let it cool (in the oven) to room temp, then do it again twice more. This will build a "patina" to the surface which is resistant to soldering.

Here's what my mould oven looks like:

http://castboolits.gunloads.com/imagehosting/thum_89094e5ad65ae2e31.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=1966)

Gear

[375RUGER]

Stay away from utube. it is for entertainment purposed only.

degrease it, preheat it thoroughly, and pour lead. Brass is beautiful to cast with. Take your time no need to rush. The mould will need to cool off occasionally. It holds heat very well.

[Seth_AZ]

Rule #1, don't put boolit lube on it, anywhere. Go to either the boolit lube forum or the mould forum (I forget which) and read the "sticky" thread on how, when, and where to lubricate a mould with the light oil.
Thanks! I just looked for and found this thread you referred to (http://castboolits.gunloads.com/showthread.php?t=137982) and read those instructions. Makes sense, and I will definitely follow them with this mold.

High-tin alloys, especially OVER-tinned alloys (ones that contain more tin than antimony, or close, or some of the type metals) are usually the culprits with "tinning" the mould. Never heard of sticking one together, but I suppose anything is possible. Your best bet is to first clean the mould really well with hot, soapy water and a toothbrush, especially the cavities, rinse well, make a mould oven and heat the mould up to about 400F and slowly let it cool (in the oven) to room temp, then do it again twice more. This will build a "patina" to the surface which is resistant to soldering.

Here's what my mould oven looks like:

http://castboolits.gunloads.com/imagehosting/thum_89094e5ad65ae2e31.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=1966)

Gear
Gear, thanks again for your comments. It's very helpful, and I appreciate it!

[Jailer]

I use an old coffee can with a notch cut out of it for a mold oven. It works well to heat the entire mold and sprue plate evenly.

Find the perfect pre heat temp for your mold and the correct casting temp for your pot and you'll cast perfect bullets from the first pour every time.

[dragon813gt]

After getting my first MP Cramer mold a few weeks ago. All I can say is run it hot and fast. I know others say to keep the lead temp low. But I had to keep it around 775 with 4 casts a minute to keep things going smoothly. With the first cast I always keep the mold closed with the lead inside for awhile(scientific right?). This is quickest way I found get the pins hot. My hotplate gets the mold hot but the pins are still to cool.

Once it's casting keepers keep going as fast as you can.


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[geargnasher]

Four complete cycles a minute might not be quite fast enough. One every 12 seconds consistently will do it with 675 WW alloy most of the time, but those Cramer moulds always seem to like running the alloy as hot as possible without drossing out the tin. At temps above 750F any tin in the alloy becomes ineffective as a flash-oxidation barrier, and this results in a higher surface tension of the alloy, not to mention a high build rate to the dross layer on top of the pot, which tends to be tin-rich and thus depletes the tin from the alloy over time. Keeping alloy temp below 750 if you care about your tin is key. If you're using an alloy with very little tin or antimony close to pure lead) then running the pot as high as 800 can be of some benefit, adjust casting pace (i.e. mould temp) to suit the best boolit quality.

Gear

[Seth_AZ]

Should I put some of the mold lube on the black pin shafts that go through the brass mold body? I don't mean on the part of the pin that goes up into the mold, just the shafts that they are attached to and go sideways through the mold block.

[geargnasher]

Depends on how tight they are. Sometimes they gum up if you lube them. Try some powdered graphite but only if you have trouble with them, the stuff used on lock cylinders, the finer the better. Or take the pins out and rub the guides with the tip of a carpenter's pencil.

Gear

[Jailer]

Yes and don't tighten them all the way. Leave them a little loose so they have a little play and will slide freely in their bore in the blocks.

[Seth_AZ]

I degreased the mold, lightly stoned the underside of the sprue plate around the sprue holes where burrs from the cutting of the sprue holes were dragging on the brass a little, and then cast up several hundred bullets. I did accidentally get some mold lube into the cavity closest to the sprue plate screw, so I had to discard a bunch of bullets with wrinkles from that cavity at one point. I figured it was easier to just weed those out until the oil was burned out than to cool the mold and clean it out with q-tips or whatever and restart casting.

The non-wrinkled bullets look pretty good. The hollow base walls aren't 100% uniform in thickness. They're close, but not 100% uniform. I don't know how this will affect the accuracy. I intend to size a bunch of these, load them up, and go shoot them in the next few days. I'll see how well they shoot. With such a very long bearing surface to engage the rifling, and the hollow base sealing the bore from hot gases and forcefully engaging the rifling, I have a feeling they'll shoot really well even if the rims aren't 100% uniform.

I did have to pop the bullets out most of the time with my fingers. That is, I had to push on the ends of the guides till the bullets popped out of that half of the mold cavity. The guides were loose after that, but I did have to pop the bullets out. I didn't smoke the cavities or anything like that.

Do you guys smoke the cavities on these brass hollow cavity molds?

[dragon813gt]

The pins loosen up over time and slide out under their own weight. I do lube the pins every now and then.


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[40Super]

I took my pins and polished the tips with unitized wheels we use at work for stainless.Once I got the toolmarks off them they drop the bullets quite a bit better. Your hollow point walls being uneven is due to the pins not being hot enough. If your fighting the bullets dropping and the pins moving ,it takes too long between pour to keep them hot enough, I have (though I shouldn't) used a small flame in a torch to CAREFULLY add heat to the pins,but you don't want to turn the tips red, thata a no-no.

[Mal Paso]

I recommend heat cycling brass molds to 400F a number of times with block faces open to air, to really develop a patina before casting. Tinning can happen at mold hot spots, typically sharp edges at the block faces. The new brass is pretty but I like my Brass Molds Brown.

[Seth_AZ]

The pins loosen up over time and slide out under their own weight. I do lube the pins every now and then.
When there weren't bullets stuck onto the pins, the pins would slide in and out on the guides very easily. I could just tilt the mold to the sides and the pins would reset. It was just when a bullet was on the pin, stuck into that pin side of the mold block, that I had to "pop" the bullets out by pushing on the guides with my thumb.

Btw, the guides weren't initially that loose, but simply loosening one of the pin guides slightly let them move freely and easily.

[Seth_AZ]

So, these hollow base walls will be more uniform if only the pins can get hot enough?
http://leigh.org/seth/some%20HBWC%20bases%20nonuniform%20walls%20web%200 035.jpg

Here's a side view of some of the ones I cast up last night. I sized one at .357" and had pretty much 100% sizer contact, and sized the rest at .358" and had maybe 30-40% good shiny sizing contact, with the rest not necessarily shiny but also far too tight to allow lubricant to migrate up the sides of the bullet under pressure in the sizer. In other words, the bullets are casting up to right at or barely a hair under .358". I'm good with that.
http://leigh.org/seth/hbwc_cast_bullets_web0033.jpg

[Seth_AZ]

Now this is a sight to gladden anyone's heart. :-)
http://leigh.org/seth/cigar%20box%20of%20hbwc%20bullets%20web%200039.jpg

[40Super]

On those the hp looks pretty good,only the outer edges on some are slightly rounded. A little more heat may help,maybe some tin? also honing a little chamfer along the top edges of the parting line so air can escape better from under the sprue plate better. I've done that with most of my molds, but it has to be a small chamfer, I hone ,not file so I can control the amount. I do it as I'm casting,so I can quickly see how it's working, if not I hone a little more , then retry. Your boolits don'tt seem too bad though so I would try some more heat and playing around.
They should shoot good as they are.