Undersized and out of round bullets, whats the cure?

[old_haidouk]

I use 92-5-3 foundryu alloy in a Master Caster with Magma molds. I get slightly out of round and undersized bullets. They drop .0005 to .001 over the sizing die diameter. What am I doing wrong? Is it the alloy? Maybe too soft, or molds too hot or too cold?

[onondaga]

If you are pressure casting, try pouring with metal a little hotter. Pressure casting when not necessary, or dead center pouring can cause out of round bullets and this will be worse with alloy or mold not hot enough. Turbulence from pressure casting and dead center pouring can cause zone cooling and failure of sprue to feed alloy to the mold as alloy cools and shrinks. Pouring from a bottom pour spout or ladle with the stream off center 1/2 the diameter of the sprue gate hole will set up a swirl to the metal delivered to the mold and this will eliminate the type of backwash turbulence that causes zone cooling and stalls sprue feed. A larger top puddle to your pour will help better feed to the alloy cooling in the mold also. Any type of casting casting with a small top puddle definitely causes more bullet shrinkage.

Round nose bullet molds and short flat nose bullet molds are most prone to turbulence but enough pressure when pressure casting or dead center pouring can set that up in almost any bullet shape.

Try increasing your casting pace or heat increase gradually till you get frosted boolits then back off marginally. Check the frosted boolits and the the ones you slightly backed from the higher heat too. See if they are round and check their diameters. Compare these to your previous results.

It is likely not the mold unless you can spot a problem on it under magnification such as metal in the vents and on the face of the mold causing incomplete closure. Or misalignment or miss-fit.

The tin in your alloy mentioned is sufficient for excellent flow and casting detail when you have sufficient thermodynamics.

Very slightly frosted boolits from hot metal and mold versus very shiny boolits from the same mold and alloy being cooler will show differences in diameter that can be as significant as .003". The hotter ones will be bigger.

Optimizing your casting technique to get the largest bullet diameter possible from your mold should help but you may require a larger diameter bullet mold. Personally, I consider .002" larger than the sizing die as an ideal cast diameter for my boolits.

Gary

[HighHook]

onondaga Well said... +1

[Bret4207]

OD- are you sure the moulds aren;t out of round?

Gary- Do you find there's much difference between casting lead alloys and precious metals? I mean other than the heat? Seems like you had the perfect training ground for casting near perfect booltis!

[Calamity Jake]

I use 92-5-3 foundryu alloy in a Master Caster with Magma molds. I get slightly out of round and undersized bullets. They drop .0005 to .001 over the sizing die diameter. What am I doing wrong? Is it the alloy? Maybe too soft, or molds too hot or too cold?

.0005-.001 over size die dia. is plenty good enough the size die will make em round.
You might be able to make them a little larger(.0005) by making them harder, and cast a little hotter causing a light overall frost.

I think Madma molds are cherry cut, most molds cut this way are
slighty out of round just by the nature of the maching process.

[44man]

A little out of round MEANS NOTHING!
Close to the size die is best, you don't need to size too much and even if the boolit just touches the die, it is better. Why deform in the size die?

[MtGun44]

Trying to figure out what is wrong with .0005 to .001 over sizing diameter?

Sounds IDEAL to me.

Bill

[lwknight]

Trying to figure out what is wrong with .0005 to .001 over sizing diameter?

Sounds IDEAL to me.

Bill

Thats exactly what I wrote in the first thread.
I don't know what kind of answer he wants.
I guess if you ask the question enough ways that someone will give
you the answer that you wanted to hear , be it right or wrong.

[looseprojectile]

must be a classic example of one to lap out. Several times I have bought bullets that were cast in Magma moulds. I always cast better more round boolits myself.
I like my boolits with square sharp bases.

Life is good

[peerlesscowboy]

Trying to figure out what is wrong with .0005 to .001 over sizing diameter?

Sounds IDEAL to me.

Bill

Sounds good to me too, and if they're a little out of round the sizing die'll round 'em out.

[old_haidouk]

Gary thank you so much for the elaborate reply.
I agree with all those that said .0005 to .001 over the sized diameter is ideal. The problem is with my set up. I use a comercial grade Lube master from Magma to size the bullets and I get a smudge of lube on the nose. Its not pressure or temperature. I played with both of them a lot and I got them down where they should be. I sent some bullets to Magma and after measuring them they said they are undersized. I use a Master caster to cast them and like Gary guessed I cast under pressure, I keep the pot full. Maybe I need to run the mold hotter. Maybe the problem lies somewhere else. I need to figure this out. A few friends and I pooled together and bought a used Lube Master(my idea) and I need to get it to lube right otherwise I'll feel like I wasted their money.

[onondaga]

Hope you try the swirl casting I mentioned. I have some molds that will only cast well that way. They are just not all the same and some times you run into a problem without ever being able to figure out why, that is why it is good to be armed with a variety of casting techniques.

Pressure casting generally works great with molds that were designed with that in mind and have the correct venting but sometimes the nose shape, ogive or length to caliber ratio changes the game to finicky and you get too much turbulence.

Gary

[onondaga]

The biggest difference in casting is that the Noble metals have much better flow characteristics and better as cast dimensional accuracy. Things like Dental implants and gold crown margins can, and are routinely made to invisible and unmeasurable fit accuracy.

Gary