Easier to cast large caliber bullets?

[oih]

I used to cast for the .45ACP and the .44Mag. I usually got good results once I got passed the initial warm up bullets. I sold those a while ago and bought a 9x19mm and a .357Mag (Fits better with my competition ambitions.). They both work great with plated and jacketed bullets, but I decided I wanted to try cast bullets too. Got out my old equipment and alloy (wheel weights + ~2% tin.), and I get som really nice bullets, but as much as 25% have such imperfections that I need to recast them. Guessing it's harder to keep the molds heated properly when the volume of the bullet is smaller.

Does enyone else experience this?

Øivind, Norway

[btroj]

I find 347 to be easy also. If I got 25 % rejects I would be looking at either the mould or my technique. Mould too cool? Poorly vented mould? Oil in mould? So many things could be the issue but I doubt bullet size is one of them.

Can you post photos of the rejects? This could help us figure out what is going wrong.

Brad

[cbrick]

Welcome to Castboolits oih,

I agree, doubtful its the caliber, they should both cast well.

Also agree to look at mold temp, too cold or too hot could cause problems. What is the pot temp, how well pre-heated was the mold?

What sort of rejects are they? Wrinkled? Rounded bands?

Agree also, pics of the bullets would help a lot.

Rick

[DukeInFlorida]

Dip the corner of your mold right into the molten lead, and let it get really HOT. Almost the same temp as the lead. Typically, you'll get good castings right from the first pour!

I'm guessing that your previous work with the larger bullets, you started with a room temperature mold, and allowed the first few pours to heat the mold up.

There's not enough heat mass in the smaller bullets to really do the job properly.

You need a hot mold before even trying to pour the first ones. That's true whether large or small bullets.

So, try the tip of the mold right in the lead trick, and see how that goes for you.

I put some Bullplate on the pivot points of the mold, and while dipping the tip, I watch for the Bullplate to start to smoke just slightly. That's when I know the mold is hot enough to begin casting.

[Guesser]

I never noticed a degradation of casting performance based on bullet size/weight until I got down to 22 caliber. I cast a lot of 85 gr. 32 caliber with no problem and 25 caliber rifle bullets worked well. 6MM sometimes were problematic. 9MM and 357 are fast and easy as long as I'm setting my temp for the mold material. steel vs. aluminum.

[geargnasher]

Lower boolit weight requires a faster casting pace to maintain the same good mould temperature than larger boolits do.

Gear

[MtGun44]

Gear is right. Think of the amount of hot lead as a "chunk of heat" being added to the mold.

Smaller "chunks of heat" mean that the mold can cool down more, so you need to cast a
bit faster. The external dimensions of a .45 or .357 mold are the same, so the heat loss
rate should be the same, but your heat addition rate is lower if you cast the same number
of bullets per minute. Cast faster to keep mold temp up.

Bill

[cbrick]

I never noticed a degradation of casting performance based on bullet size/weight until I got down to 22 caliber.

I'm not to sure that casting 22 bullets being difficult isn't just an old wives tale passed on and on. I've got 4 different molds in .224" and they all cast great, one of them is one of the best casting, easiest to cast with and one of the lowest reject rate of any of my 70+ molds.

My RCBS 55 Gr. FPGC (57 Gr. in my alloy) when properly pre-heated drops two perfect bullets by simply opening the blocks.

Casting 22 caliber bullets isn't difficult with a properly pre-heated mold and a quick casting rythm. It takes the correct heat is all. MtGun44 is right. I don't look at it as pouring lead, I look at it as pouring heat, either the blocks have enough heat or they don't. I achieve the correct mold temp by pre-heating the mold and casting rate, NOT by cranking up the pot temp.

Rick

[JeffinNZ]

My .22 boolits are just as pretty and perfect as the .303's. You have to know your mould and what it likes.

[runfiverun]

if you go from a lyman 2 cav 44-45 mold to a rcbs 35 cal mold your heat is gonna be different.
more steel and less heat per pour='s faster speed to keep the same mold temp.
aluminum is the same it cools faster than steel does.
i do run about 15-20* hotter alloy when doing 35 cal. on down to help me maintain my pace.

[songdog53]

I have found smaller the boolit hotter i run alloy and seems to work good for me.

[cajun shooter]

The best way to stop those kind of problems is to use a single burner hot plate of at least 800 watts. Put your mould or moulds on the hot plate at the same time that you plug in the lead furnace. Your mould and lead will be ready at the same time. This method provides a more even heat through out the mould than dipping into the lead. The more even the heat the better the bullets. You need to have a good thermostat on the pot or a good thermometer to see at what temp your alloy is. I turn the hot plate all the way open until the alloy is about half way and then I cut that in half. This is where I cast at. Remember that all my equipment has been checked and set up by me and you have to do the same. I doubt many $20 hot plates are able to meet NASA requirements. Once you do this I will tell you that I have less than a 4% failure rate.

[montana_charlie]

You have to know your mould and what it likes.
That's the thing, right there.
Once you figure out what the mould likes, you almost can't do it wrong.

I don't know if casting big ones is easier than casting small ones, because I only cast big ones. When you hit it right, 'easy' is too mild of a term. Fallin' off a log, slap-dab simple might be more appropriate.

I was casting smooth-sided 550 grain .45 caliber paper patch bullets.
As long as the surface contains no flaws, the only critical thing to watch is the base. It must be totally filled out so that, when you open the sprue plate, it looks like part of the mould's top ... only silver-colored.

Any 'line' visible around the edge, or any nick or wrinkle in the edge sends that one straight back into the pot. When dropped out, the base corner not only looks sharp, it feels 'harsh' as you drag your finger across it.

So ... I had the right temperatures (pot and mould) worked out, and I was using a 24 second rythmn. The sprue took five seconds to solidify, and another second to change color. At that point I would start counting, cut the sprue at 12 and dump the bullet at 24 seconds.

But, the sprue cuts were tearing a little, so I slowed down a bit and changed the sequence timing. I would cut the sprue at 20 and dump the bullet at 30.
But, the tearing of the sprue still existed.

Hoping to not confuse the mould, I slowed down again. I would cut the sprue at 30 seconds, and dump the bullet at 40. This showed improvement, and cutting sprue at 35 cured the cratering problem.

Amazingly (considering the total amount of rythmn change) the mould was still filling the base completely, and producing unwrinkled surfaces.

So ... I started experimenting with other variations.
I 'pressure poured' several, holding the dipper to the plate until it almost froze.
I poured an equal number with the mould upright, and the dipper's spout touching the sprue plate before tipping it up enough to start the flow.
Then I poured several from about half an inch above the mould ... kinda like a bottom spout pour.
Some of those I poured slow, taking a couple of seconds to fill the cavity, and for some I just sloshed it in as fast as it could go.
I poured in the center of the hole, and I swirled it around the edge.

I oriented these 'experiments' in a way that I would know their stories when I got to the culling and weighing process, later on.

As it turned out, there was nothing remarkable to learn.
The pressure poured bullets had some minor 'whiskers' near the nose.
The ones poured through the air before hitting the mould looked kinda 'frosty' in a 'swirly' way.
Of all of them (about nineteen total), there were a few that didn't quite fall into the weight range I was focused on. But they had smooth sides and sharp bases.

I discarded all of them 'just because' ... but most would probably have been just fine for shooting.

As for the rest from that session ...
Remember that they were poured using three different casting rythmns.

There were 78 bullets to be evaluated.
There were four culled because they fell well below the target weight, but they were among the first ten cast.
There were twelve that were culled for visible flaws.

The rest were visually perfect 'keepers', and fell into these five weight groups.
(my little digital scale only resolves down to even numbers in the 'tenths' position)

547.6 - five
547.8 - eleven
548.0 - twenty-four
548.2 - seventeen
548.4 - seven

Getting back to that quote at the beginning, "You have to know your mould and what it likes."

If you find what the mould needs temperature-wise, a lot of the 'machinations' you read about are simply attempts to force a mould to produce under circumstances that it 'doesn't like'.

Or, so it seems to me ...
CM

[mooman76]

I wouldn't say it's harder so much but larger boolits I find easier to cast. Mostly it just takes an adjustment in your casting such as some have mentioned, casting faster or turning the heat up some.

[oih]

Thanks for the warm welcome and all the good the replies. More heat seems to be the consensus, and I'll try to increase the temperature in both the mold and the alloy.

The rejects have wrinkles and edges that should be sharp are rounded. Also get some rejects from impurities, but that's due to being lazy with the fluxing (imo).

Also remember now that I did not use any soot on the cavities, and it was a pretty cold day in a non heated shed.

The mold is the LEE 158 grains 90303 358-158-RF

Really appreciate you guys taking the time to answer.


Øivind, Norway

[MtGun44]

Don't soot the cavities. Useless process, slightly reduces as cast diameter.

Good report, Charlie.

Bill

[cbrick]

Don't soot the cavities. Useless process, slightly reduces as cast diameter. Bill

AND you just spent your time and effort making the mold clean, why should the next thing you do is make it filthy?

It also helps plug up the air vent lines which can make casting good bullets even more difficult.

Smoking a mold is nothing but an attempt at covering up a problem. If there is a problem your way ahead of the game by fixing the problem, not by trying to cover it up.

Smoking a mold is keeping the old wives tale alive and well.

Rick

[oih]

Know this thread is old, but thought you might want to know why my bullets turned out less than Perfect; zink. :sad:

Øivind

[dondiego]

Well, at least you found out what the problem was. That always helps.