MP mold issue

[jordanka16]

I just got my first MP mold, and first hollowpoint mold, and am having a bit of trouble.

2 cavities give me bullets like on the right, perfectly filled out and crisp, the other 2 give me bullet like in the left, rounded and occasionally with wrinkles, no matter what. I have my RCBS melter cranked to 840, I preheated on a hot plate until the lube smokea, and the rounded bullets are even slightly frosted, but still no luck.

I cleaned the mold before I used it, but I'm going to totally disassemble it and do it again, but can anyone think of what might else do this? This is my first brass mold and they behave very differently.

There is some lead on the face of the blocks, but I've had that with other molds and it hasn't been an issue. Plus it's pretty consistently everywhere.

[rancher1913]

uneven mold temp, get it up to temp on a hot plate first. also some tin will help with fine detail fill out.

[georgerkahn]

jordanka16 -- I "hear" your pain. I, too, had a similar challenge with an MP mould some years back. "Listening" to a fellow on this site, I continued, and continued to cast with it. THEN -- all of a sudden -- all cavities dropped similar (but quite not as pretty as the ones you tote as 'good' ) usable bullets.
I have read, and re-read the necessary practice to bring new brass moulds up to temp; cool; bring up to temp; cool... (repeat)... at least a half-dozen times of any brass mould. This purportedly makes/puts/? an oxide finish which enables great bullet release!
I had been blackening with a Bic lighter flame; even sprayed on some commercial mould release -- neither of which helped.
Again -- the solution -- for me -- was to just keep on casting!
BEST wishes!
geo

[Wheelguns 1961]

In addition to what has been said, sometimes it helps to alternate the way you fill the mold. Front to back, next pour, back to front.

[Mal Paso]

Double check that 840F with another thermometer but I suspect the mold is too cold, gently crank up the hotplate. I run a RCBS Pro Melt 2 at 680-690F with WW alloy and most of my MP Hollowpoints.

You can check the mold temp with an IR thermometer if you put a spot of Birchwood-Casy Brass Black on it.

[farmbif]

those molds like to be hot to cast well, ive never had a problem with bullets that are frosted. but I dont sit around and look at ammo I load, I go out and shoot it.
what kind of alloy are you casting, a little bit of tin added, 2%, won't hurt anything but will be great help if your alloy is lacking tin.

[longbow]

What farmbif said ^

Plus check the sprue plate tightness. If the sprue plate doesn't swing freely it can be trapping air in cavities leading to poor fill out.

I always ensure that sprue plates swing easily... almost under their own weight and often use a jeweler's file to put a very slight bevel on the top of the mould blocks where they meet. This is a very small bevel just breaking the sharp edges but it's enough to act as a vent.

Start with loosening the sprue plate if it is tight. Then make sure the mould is pre-heated and cast fast and steady... don't stop to examine boolits.

Longbow

[Soundguy]

As the others said. the mp molds like a specific 'seasoning' cycle before you put them into use the first time.. the heat/cool/heat/cool.. etc cycles up their oxide finish.. and then after that.. as a brass mold.. like an iron mold.. they don't heat up as fast as aluminum... Lots of metal to heat.

In addition to heat.. I have found that if you are tin shy.. you don't get great fill outs.. but no need to overdo it on tin.. a little is plenty.. past that it's temperature.

[Burnt Fingers]

How much tin is in your alloy??

Did you season the mold?

Try lightly smoking the mold and pins with a butane lighter.

[GregLaROCHE]

I have a brass mold from MP, but I haven’t tried it yet. However, past experiences with steel and aluminum molds, proved the point already mentioned. The more you cast the better they seem to get.

[cwlongshot]

Still saying its all MOLD temperature. 840 is HOT LEAD!! I cast allot of HP's heat, PROPER HEAT, is key but I dont use more then 725 degrees. I have many Brass molds also more then a few MP molds. Proper heating will never warp a mold.

I know its frustrating and Im sure that YOU feel your doing right. Its human nature to blame the tool. But get that mold hot spray it out with Brake clean and it will drop good bullets.


CW

[jordanka16]

The alloy should be good, its fishing weight/WW/50-50 solder.

The common theme I hear seems to be to cycle the mold a few times, and I admit I didnt do that. I cleaned it real good again but I'll get it hot on the hotplate and cool it a half dozen times before I investigate any other issue. Thanks guys.

It's possible the mold isn't hot enough, but those 2 bullets were after 30 minutes of solid casting, plus a preheat. My big fear is to preheat the mold too much, as I've read you can warp a brass mold that way.

[Soundguy]

Multi cavity brass molds can suck up a lot of heat that can make a bullet wrinkled because the LED freezes as soon as it hits the brass so they have to be warm

[farmbif]

ive never sprayed a hot mold down with anything cold and possibly flammable. I would never, ever spray a hot mold with anything. ever. but that's just me.
the last mold I got from miha, I noticed that the machining lube that was stuck to it was not so easy to get off. I scrubbed it down with both alchohol and carb cleaner using lots of old tee shirts and q tips. it took quite a bit of scrubbing to get all the lube off. I'm guessing he is using some new high tech water soluble stuff.

[longbow]

Contrary to most, I simply wipe down my moulds when new then pre-heat and cast. If there is a lot of oil on them I have occasionally used Varsol or brake cleaner to get the majority off then I put a dab of sprue plate lube under the sprue plate and on sprue plate pivot and on alignment pins. I pre-heat until the sprue plate lube starts to smoke... just starts to smoke. This is actually a bit hot so the sprue puddle takes a few seconds to freeze. After a few boolits cast the mould temperature settles in and I can cast at a steady fast cadence. I like to just let the sprue puddle start to freeze so it is still a bit soft when I cut it. Boolits can be a bit soft too so get dropped onto damp towels.

I have several brass moulds of Mihec and Accurate and to be honest, I have never heat cycled them. I wipe down the new mould, pre-heat and start casting. Same with NOE aluminum moulds. The ones I have behave like brass moulds and like to be well pre-heated and hot when casting. I don't mind slightly frosty boolits as long as they are well filled out. Heat is your friend in my opinion.

Also, HP moulds need to be kept hot by casting fairly fast so the pins don't cool... in my experience anyway. Casting hot and fast has always worked for me.

Something to be wary of with brass moulds is tin oxide build up. There are a couple of threads about that. If the brass is very clean it is subject to tin oxide attaching. An oxide layer/patina on the brass helps prevent that. This is about the only reason I would smoke a brass mould until it develops a natural patina. I don't add tin often and normally cast plain old WW so I haven't had any issues that way but some people do.

IIRC Mal Paso above came up with a way of getting a patina on brass moulds quickly.

Anyway, that's what works for me.

YMMV

Longbow

[Wheelguns 1961]

There is a short tutorial on mp- molds website that I reccomend to anyone with one of their molds. It covers about everything needed in order to get the most from your mold.

[Soundguy]

Agreed... MP molds aren't Lyman molds.. My Lyman molds act totally differently. Might be the brass makeup.

[Targa]

I think both the bullets in your pic look great, the one on the left looks like it might have frosted just a bit but thats it. My eyes aren't what they use to be though...

[358429]

I just got my first MP mold, and first hollowpoint mold, and am having a bit of trouble.

2 cavities give me bullets like on the right, perfectly filled out and crisp, the other 2 give me bullet like in the left, rounded and occasionally with wrinkles, no matter what. I have my RCBS melter cranked to 840, I preheated on a hot plate until the lube smokea, and the rounded bullets are even slightly frosted, but still no luck.

I cleaned the mold before I used it, but I'm going to totally disassemble it and do it again, but can anyone think of what might else do this? This is my first brass mold and they behave very differently.

There is some lead on the face of the blocks, but I've had that with other molds and it hasn't been an issue. Plus it's pretty consistently everywhere.

Get the mold hot, that it takes 5 to 10 seconds for the sprue to solidify. This is the correct casting temperature range window.

Perfect fill out easy bullets dropping and slight frosting happens here.

Somewhere in this temperature range window you're going to find what works for you.

Now get it hotter, a very slight overheat. Should take about 15 seconds for the sprue plate to solidify. This is the cleaning temperature.

Get yourself a new clean white cotton rag and cut it into quarters. Use one of those rag pieces and dab it a bit with some synthetic two cycle oil, and wipe down everything, scrub all surfaces of the mold with the oilled rag.

This is the easiest and least time wasting way and least damaging way to clean the mold. The lead smears on the blocks will come right off. All the surfaces will now have a very very thin film of oil. Get back to your regular casting after doing this.

After three or four casts any oil that was in the cavities will have burned off.

Heat management is absolutely critical for the brass mold to function well.

Be safe.

Sent from my SM-G930T using Tapatalk

[Taterhead]

Get the mold hot, that it takes 5 to 10 seconds for the sprue to solidify. This is the correct casting temperature range window.

Perfect fill out easy bullets dropping and slight frosting happens here.

Somewhere in this temperature range window you're going to find what works for you.

Now get it hotter, a very slight overheat. Should take about 15 seconds for the sprue plate to solidify. This is the cleaning temperature.

Get yourself a new clean white cotton rag and cut it into quarters. Use one of those rag pieces and dab it a bit with some synthetic two cycle oil, and wipe down everything, scrub all surfaces of the mold with the oilled rag.

This is the easiest and least time wasting way and least damaging way to clean the mold. The lead smears on the blocks will come right off. All the surfaces will now have a very very thin film of oil. Get back to your regular casting after doing this.

After three or four casts any oil that was in the cavities will have burned off.

Heat management is absolutely critical for the brass mold to function well.

Be safe.

Sent from my SM-G930T using Tapatalk

Very nice. THAT is what well filled molds and crisp bullet profiles look like!