Recent 9mm purchase

[Iron369]

I’m sharing my recent experience with a mold I bought in an effort to see if others had a similar experience. I’m not complaining about the quality of my mold or the projectiles I produced with it. My results were slightly unexpected though.
I bought a MP 8-cavity aluminum .359-115gr mold offered through a group buy. My mold drops very consistent.356-124gr projectiles using straight wheel weights cast right at 700 degrees Fahrenheit. I can’t imagine what I may have done wrong, but these are my first time with a MP mold. The pictures will show the mold before I cast anything, during the casting, and my results. Any guidance from any is always appreciated.

[Iron369]

[Iron369]

[Iron369]

[Walks]

Cast at 750degrees.

What is you alloy composition ?

Do you flux once or twice? Twice for me.

[Iron369]

Cast at 750degrees.

What is you alloy composition ?

Do you flux once or twice? Twice for me.

Why at 750? I’m not being argumentative. Just asking to try and learn what difference it would make.

These are straight wheel weights.

I will flux with sawdust when the wheel weights are rendered down and I’ve skimmed the clips and junk out. Then when the pot gets low, I’ll add more weights and repeat the process. That’s to make the ingots. I will use half a tea light in my Lee bottom pour after the ingots melt.

[wv109323]

A mold maker bases the weight of a design on a specific alloy of lead. Check with MP to see what alloy that this mold should be 115 gn. Also the design may have been offered with pins to make hollowpoints. The 115 gn. may the bullet with a hollowpoint cavity and 124 without. Just a guess.

[tomme boy]

Your WW lead is more towards the pure lead side. Put some Lino type in it to add some Sb lighten up the alloy. The more modern WW lead is too soft compared to the older WW's. That is why your heavy and under sized.

[nun2kute]

It cant hurt to try casting a few at 750 to see what results you get. Depends on which mold im using as to what temp. I want. I am awfully curious why you need .359" for a 9mm pistol.

[Iron369]

It cant hurt to try casting a few at 750 to see what results you get. Depends on which mold im using as to what temp. I want. I am awfully curious why you need .359" for a 9mm pistol.

I’ll give it a try. I don’t need 359, but would size it down to 357.

[gnostic]

With PC the size should be ok, every one of my molds, Lee, RCBS, Lyman etc, drop bullets that are heavier than advertised...

[oldhenry]

I also participated in that group buy, except I chose the lube grove option. With a 50/50+1.5 alloy mine weigh a very consistent 119.4 gr.. I size to .357 & they are great performers in my SR1911 OM.

That MP mold produces beautiful boolits. With that alloy most of my molds produce boolits slightly heavier than named...…..but that's OK with me.

Henry

[gwpercle]

Maybe the lack of a lube groove bumps the weight up just as a hollow point lightens the weight .

[yeahbub]

I don't see a thing wrong with your technique or results other than winding up with a boolit 10 grains heavier and .002 smaller than what the mold was labeled for. Looks to me that the mold may have been mislabeled and you got a .356-124gr mold instead of a .358-115. If you have access to a set, you could see what diameter gage pin will slip into the cylindrical portion of the mold cavities with the mold closed. This will tell you which diameter the cavities are correct for. Might need to see about an exchange if it's a problem for you.

On the bare cast, I noticed a few that seem to have voids on the flat base. I can't see them well enough to be sure, and you probably know this factoid already, but I get those now and then and the fix is to continue the pour a second longer than it takes to fill the mold cavity. I suspect this gives time for air to escape and the not-yet-solid base to fill out with a bit more alloy. Just a thought. The "Cast at 750 deg." comment wouldn't hurt either, as it would allow the alloy to be in liquidus for a moment longer. Depends on your casting tempo - no point in waiting a looooong time for the sprue to harden. Your WW alloy might benefit from a bit of tin. Mine usually does. Some batches of alloy seem to be unwilling to fill out to sharp detail, but the pics look good. Do you cover your alloy with something to protect it from oxidation? I use a 1/4 to 1/2 inch of wood ashes to limit atmospheric contact which reduces the number of times fluxing will be needed. Sprues and reject boolits will go right through it into the alloy, no problem. The sawdust fluxing process works well, but there's generally not much ash left when the last of the wood has burned off, and if you can see the alloy, it's oxidizing. Tin oxidizes the fastest which can change the behavior of your alloy if it's marginal on tin to begin with, particularly on high-antimonial alloys like linotype or monotype. Printing houses would re-melt it and cast new type until the tin was oxidized out and it wouldn't cast sharp letters anymore. Then its off to a scrap yard, but the lack of tin was the only thing wrong with it. If the tin gets low enough, the antimony will start to come out of solution and form a silvery grey paste on top of the melt. Fluxing to de-oxidize the existing tin and adding more will get it back into solution. Keep it covered with ashes or something and the loss of tin to oxidation will be much slower.

[oldhenry]

I did a review of that now closed group buy. From the get-go it was stated that the FB & NLG would cast out in the 120gr. range. My lube grove edition is a BB (the slightest hint of a bevel base...…..I love it).
Before sizing mine are consistent @ .359.

I studied your photos & note that your boolits look good, but the part line is more conspicuous than mine (possibly because of the excellent quality of the photos). I'm not saying that your technique is wrong, but with the Lee type sprue plate I must make a definite effort to not touch that sprue lever when filling the cavities.

I hope these remarks are received as a possible explanation......maybe I should have kept my mouth shut.

Henry

[Iron369]

I did a review of that now closed group buy. From the get-go it was stated that the FB & NLG would cast out in the 120gr. range. My lube grove edition is a BB (the slightest hint of a bevel base...…..I love it).
Before sizing mine are consistent @ .359.

I studied your photos & note that your boolits look good, but the part line is more conspicuous than mine. I'm not saying that your technique is wrong, but with the Lee type sprue plate I must make a definite effort to not touch that sprue lever when filling the cavities.

I hope these remarks are received as a possible explanation......maybe I should have kept my mouth shut.

Henry

I appreciate your feedback. As well as everyone else’s. Thanks.

[tazman]

I suspect the manufacturer took into account that you would be coating the boolits with either powder coat or High Tek since that is what the boolit is designed for. I'll bet they are the right size when coated. You didn't post a measurement of one after powder coating.
This applies only to the diameter measurement and has little if anything to do with the weight.

[Dragonheart]

Actually, I think you are lucky. For powder coating I would really like to have my molds drop undersize to allow for my coating. There is no advantage of having to move a mass of metal. I have heard by many that they get better accuracy by shooting oversized bullets, but in my limited testing using a Ransom Rest I find the opposite to be true. If you slug your barrel you know what size you need to seal the bore.

I personally prefer running at a higher temperature to assure good fill out on multi-cavities.

[kevin c]

My personal impression of MP molds are that they all cast a bit heavy with my 3-2 alloy. It may be that Miha's default alloy assumption is hardball?

When I asked the honchos in the group buys, they consistently replied that the no lube groove versions of the design are heavier (of course), and that the bevel based versions are heavier as well (I guess Miha sets them up a tad longer?).

[mvintx]

You haven't mentioned how they shoot.