Why do my Lee molds cast so much easier than my MP’s?

[pka45]

It’s heresy, I know! And I’m a new caster so I’m sure it’s my fault. But my Lee molds always drop a high rate of acceptable bullets, while my beautiful MP molds take me forever to get a handful of decent ones.

I just opened 2 new Lee molds (358-158 6 cav, 41-195 2 cav) and a new MP (359-220 4 cav). I sprayed them all with brake cleaner and went after it. Three hours later, I have a bunch of Lee bullets and a bunch of frustrations with the MP! Poor base fill, wrinkles, and very hard to release (esp the one cavity I put in the HP pin).

I tried the MP first, got frustrated, tried the Lee 41 and dropped great slugs. Cleaned the MP, tried again, got frustrated again, then threw a ton of 158s from the Lee. Then tried the MP again, and got frustrated again. I used it for probably 2 hours total and still culled maybe 70% the entire time.

I know that my issues each have individual solutions, but when used side by side, why is that MP so much trickier?

I also have a MP 460-420 HP, and had the same experiences with it, over several sessions. I thought that was due to the HP pins, but this 359-220 had 3 solid pins in and that didn’t fix things. Please help.

Thanks,

Pete

[Bazoo]

I don’t know about the MP, but I’ll tell you this. My Lee moulds, the ones that cast good, rain bullets. I’ve rarely had lee moulds that didn’t drop good or fill out good.

But new lee mould I’ve had always need the sprue plate tuned so it doesn’t gouge the top of the blocks (2cavity). And I’ve had both good sized bullets and undersized. I’ve got a couple undersized ones right now.

My 452-230-2R rains bullets and has from the first drop.

Lee equals a wide dispersion of quality in my experience.

[Mal Paso]

Brass molds require more heat. Get a cheap coil style 1500 watt hotplate and put a metal plate on top. I use a 6x6" of 1/4" steel, that will get the pins hot too. There is a sheet steel cover open on the front. The temperature knob is about half way, heats the mold to just under casting temp. Some experimenting is necessary.

Aluminum has much less density and you don't need a running start like you do with brass.

[Targa]

Lee molds cast wonderfully for me as well. As for your comparison, your MP mold is a different ball game. It is brass which is a different ball game from aluminum. Brass takes longer to get up to temp but the plus side is, once you get it there it hold its temp better and will pour wonderful bullets as well. Heat that brass mold on a hot plate and that will help get you into the sweet spot a bit faster. As for the pins, HP or FP it doesn’t matter, color the pins with a lead pencil to help them release.

Mal Paso beat me to it..

[Dieselhorses]

MP molds are great but yes, they do require more heat. Somewhat heavier being brass so you have to be used to articulating a heavy mold.

[Minerat]

I run my PID at 750 for casting with brass and cast fast. Sometimes until the sprue cut count reaches 8. The mould and pins have to be HOT to get good HP forming in brass. Once you reach a point when the booolits are just frosting you can slow down. You can then slow cast at 750 with the aluminum moulds so the sprue cut count is 4 or so. I also preheat with a hot plate.

[megasupermagnum]

It's because aluminum is a superior metal to brass for casting bullets. That's only my opinion, but having cast with both plenty, I can't understand why people still make molds out of it. If you want durability, but still casts good, buy steel. I will take an aluminum mold, any maker, any design, every time.

[Texas Gun]

A good season mold will cast better then new ��
And my steel molds cast good till they too hot ��.

[cwtebay]

I know this is against what some fellas say, but I rest my brass moulds in my pot in a homemade rack. I put them there when I start my melt and can generally get a solid 20 good drops before reheating. I've tried a hot plate, but I can't seem to get my process right with it.
I do like my aluminum moulds! But my oh my can the brass ones work when you get rolling!!
And they're purty!

Sent from my Pixel 5 using Tapatalk

[pka45]

Thanks all. I did put the molds in the pot to get them heated up (up to 6-8 second sprue count) but I feel like I lost heat pretty quickly and it would drop to 3-4 seconds on the sprue. Maybe my pot temp was too low? I’ll try to work on that next time. I did get a few frosted bullets from each mold but only right after heating them in the pot.

[justindad]

Is difficult boolit ejection from the brass mold causing low mold temperatures? If so, you may need to break-in the mold through use or find a gentle way to wear off the burrs on the edges. If you’re not mechanically inclined, traditional mold break-in through use is probably all you will want to try. If you consider yourself really good with your hands, start with a strip of leather and hand rub the corners of the mold.
*
Take my advice last… I’m still learning.

[plainsman456]

I would look to the hollow point mold being to cold still.

[Gamsek]

Read the instructions on MP web site. You NEED temperature; first temperature of your mould (preheat on hot plate), then use higher temperature of ally to KEEP mould hot, even more if you are using HP mould with pins.
Its not mould’s fault, it’s operator’s technique that needs to be adjusted. Like driving cars, you “operate” your Ferrari differently then your pickup, yes principles are the same, just the way how you handle them is different.

https://www.mp-molds.com/tipstricks/...-512-mp-molds/

https://www.mp-molds.com/tipstricks/...-point-moulds/

[Glwenzl]

Similar experience only with NOE 225 gr BO bullets… IMHO with limited experience, my NOE was the hardest to learn how to use. Actually a 25 caliber Lyman was easiest (although I didn’t care for the additional weight lol) and all but one of my Lee molds have been super easy to make nice looking bullets.

My take on casting (being fairly new) is, until you have enough experience to just know, just purchase a Lee to see what you may or may not need. I have no problem with the money I spent on the 6 Lees playing with them in different rifles and hand guns. Will someday move to nicer more expensive built molds when the need/time comes. Currently enjoying the learning curve.

My only wish was that Lee had more options in the .312-316 range because I like the idea of having one mold for smaller 30 calibers to 32s.

[Bazoo]

I’ve never run a brass mould and from previous threads and this thread I likely never will. I have owned iron and aluminum and I don’t really prefer one over the other, I get along with both.

[gwpercle]

Just about every mould I've used over the years , reguardless of block material , seemed to need at least three casting sessions to get broken in and seasoned , before they would do their best work .
Acetone soak / cleaning helps pull out cutting oils - aluminun and brass seem to absorb more oil than steel but you have to clean / drive all the oils out with heat and get the seasoning done like on a new cast iron frying pan .
Also it's important to hold your mouth right when casting ... ( My Dad would tell me that ...he thought it funny !)
Gary

[Larry Gibson]

I've had several brass moulds over the years and won't get another. I only have one left. They are a pain to use because you should use a hot plate, they are heavier than aluminum or iron for that matter and you have to run the alloy hotter. I dislike making casting difficult just to say I use a brass mould. And no, they do not cast "better" bullets. I'm not criticizing or telling anyone not to use a brass mould, just saying why I won't anymore.

When I get a new mould I "prep" it first by removing sharp edges and/or burrs with stones. Then I clean the mould by spraying with brake cleaner and a bit of scrubbing with a toothbrush. When dried I use a propane torch played over the surface of the mould blocks (held open on the handles) including the cavities watching for the "moisture" to come to the surface and evaporate. When the moisture evaporates that is it. When the entire blocks have been done, I let them cool. They will be hot to the touch but no, this will not warp the blocks, aluminum or iron or brass even. When cool I swab the cavities out with a clean dry Q-Tip to remove and soot. This only has to be done one time unless the mould is cleaned or oiled again.

The mould is set on top of my Lyman Mag 20 pot while the alloy melts and comes to temp (710 - 725). With 1 or 2 cavity moulds perfect bullets drop within 2-3 pours. With 4 - 6 cavity moulds I dip the corner of the blocks it the alloy until the ally doesn't stick to the mould. Then I begin casting and perfect bullets drop after just 1 - 2 pours. I've never had to use a hot plate as I adjust the cast tempo to keep the blocks at the correct temperature for casting.

[charlie b]

Not sure about others, but, my use of a hot plate is only prior to casting or when I take a break. During casting the tempo of the process is what controls overall temp. But, I've never used a brass mold either

[tayous1]

I would have agreed several years ago after getting my first MP mold a 452. 230gr. Yet I read and asked questions like you are now and found the key several other have already said it.

HEAT you have to heat that brass up! I have used a single electric burner and It worked okay what mine really likes is the gas stove and cover it with a cast iron pan lid. As I let my lead melt I heat up the mold on low. Most of the time it comes out to hot so the first run stays liquid for a few minutes. Yet after that all my Boolite come out looking like a factory made them.

Love brass molds did but a MP aluminum mold it's okay like the brass a lot more. Give your brass a little time under some heat and you will see how nice it is.

[Mal Paso]

Brass has it's problems. Lead alloy sticks to brass much better than iron or aluminum. For casting Solid Boolits I've switched to Aluminum or Iron. If you like Hollowpoints MP's brass molds are as good as it gets. You can cast hollowpoints as fast as solids. Whatever extra mold maintenance there is, it still beats the next best solution.