serious issue with MP 38 HBWC 4 Cavity mold

[p7m13]

The internet claims that the Slovenian mold manufacturer "MP molds" sells a lot to the USA.
10 days after having mentioned, on the "MP molds" forum, a big problem with mold quality, I still have not had the slightest answer.
So I come here to explain my issue. The next tests will be done by heating the brass mold to 150 °C then more, if necessary.
Here is a copy/paste of my initial topic on "MP molds", forum where no one talks

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Hello from France.

I have been melting projectiles of all calibers for more than 40 years.

I have never experienced any melting problems, except when I used wheel weights containing a small part of aluminum and zinc.

I have molds from several manufacturers: Lee, Lyman, rcbs, lynx, and so on. My favorite molds are the aluminum Lee.

I use several alloys: linotype, monotype, wheel weights, hunting shot, lead.

I can announce the Brinell hardness of my alloy ingots before casting with a Brinell precision decimal.

I bought the MP mold MP 38 HBWC 4 Cavity mold, made of brass. This is the first time I’ve used a hollow base mold. This mold is particularly heavy. So I made a specific support.

And I have repetitive issue with it ! Problems that are repeated when I slightly heat this large brass mold with a resistor (the mold is at about 55 °C). SIMULTANEOUSLY (so same temperature, same alloy), I cast without worry 38 special wad cutter projectiles solid base with 2 Lee aluminum molds. The current alloy is 2/3 pure lead and 1/3 wheel weights without zinc or aluminum (I have experienced exactly the same problem with other alloys).

For years, I’ve been using a ladle. Before approaching the ladle of EACH HOLE, the ladle is immersed in the liquid metal.

If I want to get a proper “nose”, I have to pour the liquid quickly.

To get a nice base (the French call it “the skirt”), I have to pour the liquid VERY slowly. Probably because of a problem with air evacuation.

How do you get a perfect ball, from top to bottom ?

Any advice would be helpful. I also send this question to the manufacturer.

Regards,

[p7m13]

Two of my French friends have the same mold but for the 32 SW caliber: they succeed with their projectiles. They both use the same oven as me (Lee Production Pot IV) but use the oven bung and not a ladle

[Thumbcocker]

I have not cast hollow base boolits with MP molds. I have cast many hollow points with them, however. Brass molds like to be run hot. I turn my RCBS pot up to max and leave it there when using brass molds. Temperature can be reduced, if needed, by adding more ingots.

Place the mold on top of the pot for an hour before you start casting, it needs to be HOT. I use a bottom pour pot and pressure cast. My diagnosis from afar is that you need to make sure your mold and alloy are hot. Also, I am not sure a small ladel will hold enough alloy to fill out the hollow base on a brass mold, I don't have any experience with that set up.

Sent from my SM-G960U using Tapatalk

[JonB_in_Glencoe]

I had a MP brass 41 cal HBWC 4 cavity mold.
It seems the hotter the mold, the better, but I still never got it to cast as good as I can cast with other molds, it seems I always had some flaw in the skirt, I use a Lee pot, I've never cast with a ladle, ANYWAY, I gave up and sold the mold.

[p7m13]

La louche me permet de couler des balles 45-70 de 500 grains. Donc elle est bien assez grosse pour un projectile 38 special

[BK7saum]

Brass molds are finicky and need a lot of heat. quite a bit hotter than aluminum or steel molds. Since the HBWC has a larger pin and the skirt around the pin is thin, the pin also has to be kept hot.

There is definitely a learning curve. I have 38, 41, 44, and 45 MP molds. I cast good bullets with all, but do not get quite the keeper ratio compared to regular HP or standard molds

[Bird]

(the mold is at about 55 °C). SIMULTANEOUSLY (so same temperature, same alloy).

55C is not near hot enough for a mold. 200C maybe.

[muskeg13]

I have .32, .38 and .45 4-cavity HBWC MP molds. I use a 20# Lee ladle pot set between 800F and max temp, and I use a lead thermometer to maintain about 750F during the session. All molds, including the HB pins are smoked with wood matches while the alloy is melting. The smaller .32 HBWCs cast pretty easily once the mold is hot enough using 1:20 alloy. It was more difficult to get good .38 and .45 HBWCs for two reasons. First, I went with a softer alloy, 1:40 because I was also casting .45-70 and .50-70 boolits for BP, and I wanted to make sure the HB skirts would expand. The .32 S&W Long I cast the .32 HBWC for has a very tight bore for a .32 (.310), so skirt expansion isn't needed for obturation, so a harder alloy/less skirt expansion isn't a concern. Another problem with the larger HBWCs is that my ladle doesn't hold enough alloy to fill all 4 cavities with one pour. With the .38 HBWC mold I ended up filling 2 cavities at the time, and as long as I was quick about it, I started getting good skirt fill-out once the mold was hot enough. As for the .45 HBWC, I had a difficult time getting good fill out. It wasn't until late in that casting session I finally started consistently getting good fill-out with 3 of 4 cavities. The next time I cast HBWCs, I plan to have more tin in the alloy.

[Driver man]

Preheat the mould really well until the lead takes around 10 or more seconds to solidify on the sprue plate. Miha recomended 415C/780F.

[Shiloh]

What does the HB look like?? A concave or a hole like Meister Bullets HBWC??

Shiloh

[muskeg13]

What does the HB look like?? A concave or a hole like Meister Bullets HBWC??

Shiloh

MP HB are deep cone shaped depressions like factory swaged HBWCs. My flawed boolits almost always have a single large crease in the skirt. Not hot enough mold /pins?
I've loaded or shot up all of my MP .312 HBWCs, but these are the .358 and .452 MP HBWCs:

[muskeg13]

For years, I’ve been using a ladle. Before approaching the ladle of EACH HOLE, the ladle is immersed in the liquid metal. If I want to get a proper “nose”, I have to pour the liquid quickly. To get a nice base (the French call it “the skirt”), I have to pour the liquid VERY slowly. Probably because of a problem with air evacuation. How do you get a perfect ball, from top to bottom ? Any advice would be helpful. I also send this question to the manufacturer.

Your problem probably isn't the mold design or a manufacturing defect. Hollow points and especially hollow bases are much harder to cast without defects.

Suggestion: Once the alloy and mold are both very hot, go back to your normal technique of pouring fast with the ladle spout in loose loose contact with the sprue plate opening (allowing air to evacuate), but continue forcing alloy into the cavity for a few seconds until quite a bit of alloy flows out of the cavity and over the sprue plate and back into the pot. Hopefully this forces out the air in the cavity and forces alloy into the mold crevices to completely fill out the skirt. I agree the problem is air evacuation, possible compounded by too low mould and alloy temps.

Many years ago, a seasoned boolit casting friend showed me an article entitled "The Standing Wave" referring to surfing I guess, but more the principle of trying to force more alloy into the cavities to force air out of the cavity recesses. This creates a "standing wave" of fluid alloy on the sprue plate that quickly runs off. After understanding that technique, I've been able to cast better hollow point and hollow based boolits.

[pjh421]

All good advice. Without using your mould myself, I can't specifically diagnose much. Consider this though, and my appologies if my answer is somewhat redundant and or obvious to you. Chase any vent lines with a carbide scribe if that is possible. I don't do it on moulds with the Lee style venting but moulds with traditional straight line venting are easy to correct with the scribe and some magnification. Your mould, any pins and sprue cutter should be squeaky clean. Degrease them with non-chlorinated brake cleaner. Then proceed to coat them with clear automotive silicone dielectric grease and wipe off any excess so that only the thinnest film remains. This will prevent any lead alloy from sticking and boolits will drop out very freely unless there are other problems like burrs. You need a hot mould and sprue plate (careful to not warp the sprue plate). I pre-heat iron and brass moulds on a hot plate near my casting pot. This is much quicker than heating the mould using the pot. Also, if you leave the hot plate on while you're casting you can periodically adjust the temperature of the mould in short order as you see problems developing such as wrinkling. I have a 477640 group buy brass mould from MiHec that needs not only this treatment but also requires me to keep an electric heat gun within reach so I can adjust the temperature of the nose pins. This mould likes to be run hot. In fact, there is such a narrow window between too cold and too hot that I caused an alignment pin to walk out one day. This is not one of my favorite moulds because it requires all this extra attention but it does make good looking boolits that are usually within a grain or less of each other. I hope you sort this mould out. Sorry if I'm only telling you what you already know.

[MT Gianni]

When I dip, I use a dipper large enough to fill all cavities and leave a generous sprue.

[country gent]

1) you need to be a little hotter than for plain based bullets
2) Pour fast an fill the cavity quickly
3) pour a large generous sprue

Several little things that may help.
make sure vent lines are clean and to depth.
with a fine stone form a small 45* bevel on the tops of the blocks just .005-.010 on a side. This makes one more vent line right under the sprue plate.
If your ladle casting try opening the ladle pour hole to .200 dia to get a faster better fill.
The other thing is to cast with 2 moulds giving them time to pull heat and completely solidify. This works well as you arnt waiting on a sprue to solidify as your filling the next mould. And its pulling all the heat from the full cavities.

[gwpercle]

When using a dipper ... keep the dipper in the casting pot so it stays as hot as the melted metal .
If the dipper cools off ... it will cool your metal as it flows into the mould ...
giving imperfections .
Do Not take the ladle out of the pot while cutting sprue and opening the mould .

Gary

[26Charlie]

I have only 2 brass moulds, and find that they have a high rate at which they cool off the lead cast. I have been able to get better bullets if I smoke the mould. This is just taking a candle (little birthday candles are handy for this) and letting the flame deposit carbon smoke in the mould cavity. A few casts will clear out any non-carbon volatiles, and then the bullets should start coming out without defects. The finely divided carbon smoke particles seem to slow down the cooling rate. This works with difficult aluminum moulds too.