MP 413640...what am I doing wrong?

[blueline541]

Having never owned a brass mold much less one with pins I read up on the none ending discussions about the best way to prep a brass mold. I went with the less is more side of the argument and bathed it in mineral spirits and gave it a scrubbing with a toothbrush like I've done with all my other molds. In ten minutes time the mold began sticking together while attempting to drop bullets. Now I have a pretty good lead outlines on all four cavities inside the mold blocks.

So, what all do I need to do with a brass mold to make it work? Treating it like my iron and aluminum molds has now made this one useless in record time. Had multiple people not mentioned having success with a simple cleaning then I wouldn't have done it this way.

[06ackley]

I just used mine and made a couple hundred boolits in an hour.What I did to mine was I scrubbed it with dish soap and a toothbrush then I sprayed it with some brake cleaner and scrubbed it again.Then I did three heat cycles to it. I also made sure the pins were burr free. I did notice that the mold likes to be hot in order to work good.It is definitely different than my aluminum molds.

[Sgtonory]

Clean your mold again. Then heat and cool your mold a few times to get it to oxidize. M

[RED333]

I do not have this mold, but do have a few brass molds.
Clean it as above, soap and water, heat cycle it a few times.
The lead stuck on can be removed.
Get the mold HOT, rub the lead with a piece of hard wood,
most will come off.
As others have said, brass molds like to be hot to cast well.

[**oneshot**]

I take it apart and clean with dishsoap and a toothbrush, rinse well and dry it. Cycle it through the oven at 450 for 3-4 cycles cooling it for an hour or so (room temp) in between heatings. I do this to all my molds before trying to cast with it.

[longbow]

I do very little with any of my moulds, brass, iron or aluminum and have very little trouble casting. I just wipe them down with a rag, use some sprue plate lube on pins and sprue plate then pre-heat until the sprue plate lube just starts to smoke... that's "just starts" to smoke a little.

I get few rejects even with new moulds by ensuring good pre-heat. I oil all my moulds after use ~ yes, even brass and aluminum moulds because they have steel pins and sprue plates. I do not like rust! Again, I just wipe them down, use a bit of sprue plate lube then pre-heat until the lube just starts to smoke then cast away.

I am going to suggest that if you did not use sprue plate lube on the alignment pins that may be why you are getting a gap and lead between mould halves. Very lightly oil the alignment pins and if a Cramer design oil the sliders and a bit on the HP pins where the mould halves close on them. Use a Q-Tip and sparingly wipe a small amount of oil on each part.

Another thing that came up in a different thread was that some people are getting "soldering" of alloy to their brass moulds. If you are adding tin this may be a problem. I never get soldering but I seldom add any tin. I cast with hot alloy and hot mould to get good fillout.

If you do find you are getting soldering/tinning on the mould, there is a thread about adding a patina to the brass to prevent soldering/tinning. Do a search and you will find it. It has never been a problem for me so I haven't bothered.

Sometimes a new mould will take a bit for pins to seat in so now and again if I see a bit of a gap I will tap the blocks lightly with my sprue plate dowel to ensure the blocks are fully closed. That is lightly tap not bludgeon. Often they need help seating until things smooth up some.

Don't despair, MP moulds are works of art and cast very well. There is a bit of a learning curve to get the hang of them though and brass moulds do like to be cast fast and hot.

Longbow

[RED333]

Sometimes a new mould will take a bit for pins to seat in so now and again if I see a bit of a gap I will tap the blocks lightly with my sprue plate dowel to ensure the blocks are fully closed. That is lightly tap not bludgeon. Often they need help seating until things smooth up some.

Don't despair, MP moulds are works of art and cast very well. There is a bit of a learning curve to get the hang of them though and brass moulds do like to be cast fast and hot.

Longbow

As it is second nature I had forgot about the tap after I drop out the boolits.

[blueline541]

Thanks for the suggestions. I'll get the lead off of it and try the scrubbing and heat cycles and give it another go. It was disappointing to say the least, but I put the H&G on the hotplate and salvaged the day with a nice pile of SWCs.

And I do agree. An MP mold is a work of art. It really is amazing.