Brass mould .........is it always like this ....

[RBHarter]

So some might have read my struggles with an MP brass 462-420 .....

Very excited about this mould , it was a trophy mould . I followed all of the break in suggestions and procedures and after 7-8 runs and a dozen or so heat cycles ....... appearently the desert west isn't real forthcoming with brass patina .

Moving along , I had it running slick 1 PB 1 HB , 60 pours for 50-55 keepers of each , yeah buddy . Not to let success keep me from being critical of the success I noticed that the PB was stepped a little bit on the base . I really need to stop reading all perfect base/match weights/etc . Too late for that . I looked it all over and flipped the PB pin and changed out the HB for the other PB and checked it both ways to ensure the it would be flush not extended and installed . Put it on the Lee handles and stuck it in the hot plate hot box . I topped off the heating up pot with rejects from the last batches of my 50/50 WW-1/20 +CU and waited fussing with some no box singles and looking for a means to box them up for the pending June move .
With the alloy up to the nominal success temp of 725-735°F , the mould and ladle up to temp too I set about pouring 5# or so to keep me with busy hands when I need to think or detox from the workplace .
The first 5 pours are ugly so back to the pot with sprues .
The next few pours looked good as the mould opened , just a glance of course . So I poured till the ladle needed 2 trips to get sprues and 2 bullets and slipped the mould back in the hot box and topped off the pot with sprues and the first 10 .
Then I did some quick QC ......... I saved about 10 of the first 75 .......
Whatever . Back in the pot ye briney naves , meet thy doom .....or something equally silly , the Remmy dog likes the pirate routine .
Hey electric cleaner maybe that'll fix the dirt weep in the grooves messing up the bands ! .........nope and after the 2nd run the carb cleaner wasn't any better . Smoke from a wood match was no help either . At some point I noticed a lot of floating junk and skimmed it off , I also added more alloy , stir , flux etc by my routine . After about the 4th cycle and over a lb of what's that skimmed off everything settled down and ran like it did before .

This is the only brass mould in the stable an at this point it's a Premadonna . If it were an NOE aluminum or a Lee or a Lyman even I'd have probably thrown it across the street by now . I mean it's like a racecar it either runs like a Swiss watch or a Yugo car . Are they all like this do they ever settle down so you can open the box mount the handles warm it up waiting for the pot or should I figure on making 250 pours and only keeping 200 or so bullets or could it have been something I picked up in the alloy ? Like a lb of cerro cast ? Maybe I got zinced from old alloy ? Does this mould maybe just have an aversion to tin or copper ? Can the copper fall out of solution ? Does the tin/copper solution of the 1/20 tin/pure not play well with the brass mould ? Im at a loss .

 

[Brad]

Got any photos of the problem bullets?
If you are getting rounded bases then a light, and I mean light, breaking of the top inner edges of the mould may help.
Many moulds are so tight that air can't escape well enough and it causes a base deformity, usually a rounded base.
Take a fine file, hold it at a 45° angle and take a single extremely light stroke on upper, in return edge of blocks. Even better might be a medium to coarse stone. If you can easily see the envelope you may have gone too far.

Some photos would really help a bunch here.

 

[uncle jimbo]

Is the mold a 2c or 4c? Because I have a MiHec 4c mold that acts just like what you described. I have cleaned it numerous times, run it super hot, not so hot, and everywhere in between. The end cavities always seem to leave round bottoms or air pockets. I quit running it with the HP pins thinking this might be the problem but it does it with the fn pins also. I did find that if I only keep the two inter cavity bullets they always look good. Sometimes I can keep the outer cavity ones, but I stopped worrying about them. I now just think of it as a very expensive 2c brass mold. I'm getting too old to be obsessive about something that is suppose to be enjoyable.
If you do run across a fix for yours, please pass it along.

 

[358156 hp]

I have a recent 2 cavity MP mould. After much frustration, I finally forced myself to take a fine cut file and break the edges at the parting line to get good bases. This did help the base issue a lot. A single very light pass over each top parting edge. You probably won't feel like you removed anything, but you're just trying to create a tiny vent, that's all. The issue with only getting good casts with the outside cavities is almost a textbook symptom of inadequate base venting. One other issue I've noticed, when you preheat your mould, make sure you get the sprue plate really hot as well, I've seen some guys give MPs heavy sprue plates a lick of heat from a propane torch to bring them up to temp. A sprue plate that's not up to temp can cool the sprue slightly, and that can mimic or exacerbate (big word) incomplete base venting and/or fillout. Excess oil (like Bullplate for example) can affect venting too. Use lubricants very sparingly.

 

[gman]

I have one MP brass mold and have found it to be a different animal. I find I need to preheat this mold at a higher temp than my aluminum molds. I set my hot plate a little over medium while my alloy is melting. From there I cast as quickly as possible. I’m not satisfied with it yet but I wanted that mold based on reviews. Personally I’ll take an Accurate mold any day over these. I understand if your wanting a hollow point Accurate doesn’t supply. Good luck!

 

[Ian]

Accurate brass moulds have always been easier for me to use than MP as well, but both work fine if you can manage the heat.

 

[gman]

Brass molds are definitely a different animal than the aluminum I’m so used too.

 

[RBHarter]

I ran all the junk back into the pot .
It's a 2 cavity nose pour with plain base and hollow base pins .

It's the oddest thing the alloy pours in high definition with every tool mark visible in the cast except that the bands don't want to fill out mostly on one side . The pins stay hot nicely and the it was almost like it had oozed oil out of the pores or something .

I thought as another possibility that it just had to be heat soaked through to work it's best.

 

[RicinYakima]

Agree with 358156 hp. They are soft and will not take abuse. (Were they made for Lee handles, seems like a poor choice if it were). I run mine about 685 degrees by the PID controller with WW's +2% tin; one is a Mountain Mold 2 cavity .45 acp and the other is a .40 BPCR. Pictures will help.

 

[RicinYakima]

If they aren't filling out on the side that first gets alloy, it is too hot. Brass ain't aluminum.

 

[Rick]

All of my MP brass molds are a dream to cast with. Brass does take more time & effort to get up to a proper casting temp but once there I have no problem keeping them there. Sounds much like a mold temp thing to me and as was mentioned the sprue plate HAS to be kept hot. You cannot get good base fill-out with a too cool sprue plate any more than you can get good HP nose fill out with a too cool HP spud.

Iron, aluminum and brass molds all cast differently and each must be learned. There is a learning curve with most everything new, brass is no different.

 

[Rick]

(Were they made for Lee handles, seems like a poor choice if it were).

MP molds are made for LEE handles but Miha makes his own much higher quality handles than what LEE offers, either can be used.

 

[RicinYakima]

Thanks Rick! I don't own any MP or Lee moulds. I do have a set of Lee handles I threw under the bench because they didn't fit any mould that I own. They were so sloppy that they just beat the faces of the mould up or dished the alignment pins.

 

[RBHarter]

B&W to remove some of flash brightness.
I saw something about getting too hot and not filling out well .

As seen the bases look good even the hollow base .
The nose gouge is actually a flat cut with no divit I don't know why it looks like that .

The mould . I see that it has some spots on the band points . I have a little bit track and smear on farthest cavity sprue but it's just a haze on the plate and discolored maybe on the block top.



As for lube I used NOEs on the outside end of the slide pins hot mould closed . Thumb smeared to discolor the sprue plate and a touch to seep and walk from the outside of the screw head to the plate . The pins got some from the Q tip that soaked up the extra from the slide pins . Out of habit I hit the handle screws with a little on the threads because I hate that steel aluminum galling and brass doesn't need it but .......habits .

I didn't notice how scruffy looking the mould is , it's like it's a tool or something and I hadn't cleaned up the bench from the last run or something .....

 

[RicinYakima]

Mould is too hot at that spot. Lower temperature and slow casting pace. FWIW, Ric

 

[3856imp]

Watch out for tinning, copper loves Tin. It looks like some is building up and closing your lent cuts

 

[Rick]

I agree with Ric, alloy pulling away from the edge of the middle driving band could be the mold getting too hot, I've got SAECO iron molds that are notorious for that. The base and HB spud could well be from the spud too cool. HP noses look like that when the spud is too cool.

 

[fiver]

those are for sure too hot of a mold.
brass retains heat like a champ.

you got zero patina in those cavity's.

anyway try getting the mold up to temp and then just dribble the alloy into the sprue holes.
don't swirl it don't pressure it.
just dribble it on the edge of the sprue plate and let it run into the cavity's,,,,, a one th--- one- 2 tho---2 count might even be too fast.

 

[Ian]

you got zero patina in those cavity's.

This.

You're in that "awkward stage" of mould temperature: Too hot for shiny bullets (badly frosted, shrunken edges) and not quite hot enough for a smooth, satin frost on the bullets. That mould should be antiqued by now with all you've done to it, yet it looks brand new. As hot as I run them, they get antiqued in one session. Not saying thats how you should do it, just saying how I do it.

If you run up the casting speed until the mould starts throwing sharp, lightly frosted bullets, tinning is apt to occur at first because you have so much of it in your alloy. To mitigate this, I use a butane lighter to put just a whiff of caramel-colored smoke in the cavities, no more than that. Matches have the sticks coated with paraffin to keep them dry and to keep them burning once the head fizzles, so match soot has oil in it. Propane soot does not.

 

[358156 hp]

I'm working with a borrowed Accurate mould that's having similar issues. It has three cavities that are around 350 gr, and two that are over 500 gr. I got the alloy issue stabilized (too much tin), and now all that is left is to give it what it seems to want for cadence. I'm adding another mould in to slow my cadence down as this big mould heats up, it heats really quickly with over 2000 grains of hot lead inside. I need to give it more time to cool. My driving bands looked like yours do, frosted and rounded. The other give away for me was pulling sprue plugs from the bases.