Possible zinc contamination on cast bullets

[Reefinmike]

Im hoping it is just that my first batch of cast bullets were newbie mistakes, i hope from simply just a not hot enough alloy and mold. I cleaned upmthree different batches of wheel weights.

Batch one- i tapped every weight on a set of bolt cutters. If they didnt sound soft, they were thrown out, if they were suspect, they were run over a magnet. If they didnt stick i attempted to cut them. If they werent cut easily, they were tossed. I might add that i without reading up, added about 15-20%stick onmpure lead ww's. About seven pounds

Batch two- i simply looked for gouges in the ww's- a new method i read up on. If it was gouged, it was thrown in the good pile. If not, tapped cut blah blah blah. About thirteen pounds.

Batch three- used same method as batch two until halfway through when i came across a zinc ww with a decent gouge that looked very similar to a lead and the coating caused a lead like thud. I then went through every ww, of it didnt have a significant obvious lead gouge, i clipped it.

My first batch of bullets, the suspect ones were 102 gr 380's in a lee double mold. At first i thought they looked good. I rejected about 20% out of 500. Looking through the "good" ones that i used batch two lead, they now look terrible to my most recent casts with batch 3 lead. The bottom edge is rounded on many and not sharp, lin general, not smooth and shiny. Many ofnmy accepted ones have some slight wrinkles. I casted 500 38 spls using batch one lead and they all turned out beautifully, only 10 rejects due to the mold not lining up

Just now i casted some 380s using batch three lead and they came out very sexy, no wrinkles, shiny boolits with sharp defined groves and tail end. Only had 5 /600 rejected due to incomplete fills

Also, i should mention that the suspect batch of 380's have a gritty looking dimpled in sprue plate cut. So, do you think that slight wrinkles, rounded bottoms and a rough sprue plate cut are from zinc contamination or just newbie casting and i should re-melt them?

 

[Shadow 7D]

OK
so it comes down to this, is it worth the effort to recast, or are they good enough?
if they load and shoot, and aren't that accurate, for plinking...
or, you recast and try like hell to use temp control to keep to JUST melt the lead (I think this is a problem due to it making an alloy or modding the melting point, so, I guess, you need to asked a person more experienced. Check out Castboolits.com I think they have a sticky on this.

 

[evan price]

I assume you are NOT smelting raw wheel-weights in your casting pot? That way you keep the dirt and crud out of your nice clean bullet melter?

Sounds to me like your casting alloy temp was too low and your molds were cold.
The wrinkles and the lack of a sharp base shoulder say that.
The "gritty" cut at the sprue- perhaps you cut the sprue too quickly. You need time for the sprue to harden and draw lead down into the base of the boolit before you cut it.

The smaller the weight of the bullet, the less molten lead there is to carry heat into the mold. So the mold heats up slower. I find when casting Lee 105gr-SWCs in 6-cavity that the first ten or so casts are going to be rejects. As compared to Lee 240gr-SWCs in 6-cavity that the second or third cast is usually all keepers. One way to help get started is to preheat the mold- a hot plate helps, or you can dip a corner of the mold in the molten lead. I leave my mold sitting on top of the casting pot while it comes up to temp, that preheats the mold nicely.

Zinc is the big boogeyman of newbie casters. There are three ways to deal with zinc-

First- don't get it in the pot to begin with when you smelt; start a new melt with known lead only, then wait until the pot of alloy has temp-stabilized before adding unknown material. Your method of checking weights works but is slow. Instead of squeezing, may I suggest you setup a way of bendingthe weights? A bench vise, a pair of pliers clamped to a table top, etc. I find lead weights can be bent, zinc ones can't be, and that's less hand strain than squeezing 500 wheel weights...

Second- keep your smelt temperatures at around 700 degrees; Zinc melts closer to 800 degrees so if you are at 700, the zinc just floats.

Third- if you suspect zinc, remelt the alloy at 700 degrees and hold it there, flux with a carbon based reductant flux (Anything with carbon- oil, paraffin wax, sawdust, etc...I use drained motor oil from my oil changes...works well, and free) and stir well, and skim off any oatmeal dross.

Now I'm getting into technicalities...there are two basic types of fluxes. There are reducing fluxes and there are slag-forming fluxes.

Reducing fluxes contain elements that react by removing oxygen from the alloy in the melter. Hydrogen and carbon are higher on the periodic table of elements and more reactive than lead or tin. So the lead and tin oxides give up their oxygen to the more aggressive carbon and hydrogen, which is consumed, leaving behind the raw tin, lead, etc. Good reducing fluxes are things like hydrocarbons, motor oil, fats, candle wax/paraffin, sawdust, wood shavings, etc.

Slag-forming fluxes are intended to act as a filter or barrier. They melt and form a crust on top of the alloy that prevents new oxygen from reaching the surface of the molten alloy, and also encapsulate and trap any contaminants that might be on the surface of the alloy. The slag is skimmed off and takes with it any trapped contaminants ("dross"). When fluxing it is important to reduce first because tin oxide will be skimmed off in the slag and tin is the most expensive element in bullet casting alloy. If you reduce the tin oxide back into elemental tin using a reducing flux, you won't skim it off in your dross. Marvellux is a slag forming flux.

One way to test for presence of zinc is to take a cooled sample of an unknown alloy and apply a bit of acid. I like to use acid toilet cleaner called "The Works". Acid and zinc makes a foaming reaction, like vinegar on baking soda. If the metal doesn't react, it isn't zinc.

You can have a percent or two of zinc contamination in casting alloy with no ill effect except for bullets being a bit harder, a bit lighter, and not filling out fine detail in the mold. Zinc is sort of an "anti-tin" in how it behaves in a lead alloy.

 

[Reefinmike]

Wow! Thanks for all the info evan. Im using a pair of large lock cutters to clip the suspect ones, much easier than bending, especially since most weights are under three inches. Yes, im using an old pot and propane burner to melt down the raw ww's. Can you really skim off zinc if a contaminated alloy is remelted? I thought once zinc was melted in, it was trash.

 

[Dthunter]

If your melt looks like porage, and you thermometer says
You are up to temp, your alloy is contaminated. Junk it! And just be careful
Next time. Been there/done that.

Just watch for the floaters when melting the wheel
Weights. Skim them off and your good to go. After you do a few more lead pots, you will get the hang of It.
I ruined one pot of 80lbs of alloy! I learned my lesson! I've casted close to a ton of lead since. Just keep at it.

Evan price has allot of good info. But that kind of indepth detail just isnt nessesary for the casual caster. Keep it simple. (no disrespect to EVAN).

If you like learning like I do, soak it up! And join the cast boolets site. Its a major wealth of info!

 

[Dthunter]

If you try to seperate the zinc, it takes a nasty series of fluxing proceedures. And it gives off nasty, NASTY, poisonous,complex chemicals and Carcinogens! Not worth the bother to me!

 

[RustyFN]

Evan covered it pretty well. I'll add that sometimes you will need to add a little tin to get nice square shoulders. A little tin will help fill out in the mold better. I cast with straight WW's and will add to a 20 pound pot 2 to 3 feet of 1/8" round 95/5 solder. That's 95% tin and 5% antimony. It doesn't take much. If you have zinc contamination in the lead the bullets will look like oat meal.

 

[Reefinmike]

Well, no oatmeal was seen besides in my pantry. After casting another 1500 perfect ones today with only 4 defectives, i think ive got it down. I think i was just going too slow, and didnt keep the right temp. Its amazing that stopping for literitally one minute makes reheating the mold necessary

 

[RustyFN]

Glad you got it figured out.

 

[OldTex]

A classic resource for everything to do with casting: Cast Bullet Guide for Handgunners

 

[Reefinmike]

Well, i just killed two birds with one stone, removed the way too thick coat of alox(nasty nasty tar like junknfloating on top. Ruined my fluxing spoon) and made the bullets much prettier! Im really not sure what exactly i did wrong to make the rounded out shoulders rather than a nice straight square shoulder.

A couple things i did learn today after nearly 2k casts- proper temp of melt and mold is vital. Also, on this last batch, i learned that if you smack the sprue the instant the lead isnt wobbley wiggley on top and is still shiney, it makes a cleaner cut, and immediately after the bullets drop much easier. Before, when i let it harden a second longer, it would take three smacks to the bolt to drop the bullets.

Im just happy i havent had any zinc mixups. Now time to play with adding tin solder to the 20+ lbs ofnpure lead stick ons i have. May just try 75% stick-ons, 25% clip ons for use with really light 38spl loads(3.4gr win321 under a 158gr swc)

 

[cheeze]

For pistol bullets, I always just melt ALL the weights, flux, and skim off the zinc. Never had a problem making good bullets this way. If I was trying to make competition bullets, I would be a little more particular about it, but don't get upset if you get a lil' zinc in the mix. I never had it cause any problems.

 

[Reefinmike]

Cheeze- i would do that but i dont use a therm on my melt and with how few ww contacts i have, id hate to spoil a twenty pound batch-aka 850 38 spls or 1350 380's. When i have multiple bucketsmof ww's laying around, i may do that

 

[cheeze]

I don't see how you would spoil anything. The lead is heavier and will be at the bottom, and the zinc will skim off even if it is melted. It won't hurt your .38s or 380s. I melt it all... whatever doesn't melt is steel/iron. The zinc looks like overcooked oatmeal at the top (except it's grey and gets a purplish iridescence to it). It will skim off and separate from the lead easily with a slotted spoon or whatever skimming device you use. The lead will drain out of it as you lift it out of the melt. You can tell when it's gone, because the top of the melted lead will be nice and mirror shiny again. It's easy to remove.

 

[evan price]

Yes, you can skim the zinc out of your alloy. Takes a lot of time and careful regulation of the melt temp. I've done it to batches that I let get a little too hot and I started skimming out half-melted zinc weights. Reduce the pot temp to 700 degrees, skim off all the clips and other junk, then flux and stir and skim out the oatmeal looking stuff. It will be dull silver and won't flux back in with anything.

You won't get 100% of it out, but you can save a batch that way.

There's also been good results fluxing with sulfur at higher temp. This however makes very dangerous fumes and requires some care.

 

[popper]

Spoon is not ruined, it'll burn off. Try pressure pouring to get square shoulders. 75/25 will work good. Try for 1:1 of Sn:Sb, if you use 95/5 solder it's just adding tin and you don't need much. Go to cast boolits and get Bumpo's alloy calculator.

 

[Old Rock]

Thermometer

Hi, I cast many bullets without issue for years when I was in the service (a long time ago). I had a Lee production pot and both Lee and Lyman moulds. I now have a new Lee production pot and some new Lee moulds. I got a lot of wrinkles in almost everything I cast. It was a little irritating as my kids have finally gotten out of the service and I was trying to show them how it was done because they were very interested. After a few pours the lines seemed sharp but there were still wrinkles in the bullets. I am curious if anyone would comment as I tried a couple of different settings on the controller and am pretty sure it was hot enough. Also, what are folks using to measure the temp? That sounded like a good idea as I have also been finding the zinc wheelweights in some of what I scrounge up. Thanks for your thoughts.