Casting

[crummyshooter]

It's probably been discussed in the past, but I'll put it out there again.

I am casting 405 grain hollow base .459 bullets in a Lee alum. mold. It seems that when I get the temps right so there are no wrinkles the bullets start out at a littler over 409 gr and decrease in weight as I continue. Just now I cast 10, They decreased from 409.6 to 405.7.

I've never run a long enough batch to see if the stabilize, at some point.
Ideas?

 

[Missionary]

Good morning
Is your mix getting hotter all the time you are casting ?
Are you changing something in the mix ?
Molds will change as they get hotter. Aluminum expands and contracts like all metals. Plus you have a steel base plug that also is getting hotter.. expanding.
What we are always looking for constants. Keep mold about the same temp. The mix the same temp. The ingrediants in the mix the same amount.
Mike in Peru

 

[crummyshooter]

Thanks

I was thinking maybe the mold was cooling. I have been letting the bullet set for 30 seconds befoe dropping it. Maybe too long.

 

[KansasSasquatch]

I'm new to casting myself and my only experience is with a Lee .452 230gr TC tumble lube mold. I only let the bullet cool enough so that the sprue is solid before dropping it, less than 5 seconds. If it takes the bullet longer than that to cool I think the mold is too hot. So far I've had pretty good luck. My boolits have been coming out right at .452 and with my alloy the weights have all been between 234gr and 236.5gr with 90% of them being right at 235gr. That's with me weighing about 125 out of 800 or so boolits.

 

[grubbylabs]

I won't swear to this with Lee molds but it is a good chance that they designed the mold to drop the advertised weight based on Lyman #2 alloy. Your WW mix is going to vary from that some.

This is where having multiple manuals and making educated guess come into play. You should cast a couple hundred bullets and figure out a rhythm and cadence that works for you and your gear. After you get a good cadence and rhythm down you should be able to get a consistent weight on your bullets so that you can figure out some loading data. Also remember that not all cast let alone jacketed bullets are going to be the same just because they way the same, or are close. Your C.O.L is going to vary from one to another.

If you are casting at a steady consistent pace you should have no problems keeping your mold up to temp. Each mold is different even when they are from the same maker. You are going to have to spend some time figuring out how hot your mold likes to run. Bring every thing up to temp and start experimenting with melt temps to see what the coolest is you can run your melt. This will allow you to keep the alloy consistent and help your mold from getting to hot.

While there are quite a few on this forum who know quite a bite about casting, I would still recommend visiting the castboolits forum. Cast bullets are what they do.

 

[USSR]

If you're expecting your cast bullets to come out of the mould at the same weight, you're gonna be disappointed. The variance in weight you are seeing is normal and nothing to worry about.

Don

 

[Springfield0612]

USSR is right. If you weigh commerical bullets and even commercial cast bullets you will see the same variance. People who shoot competition use MATCH GRADING and weigh every component and separate them into categories that are similar weights. Brass, bullets, heck some may even weigh the primers. If shooting different weights is an issue for you I would suggest doing the same.
Another way would be to learn your mold and your alloy. Ensure you have good thermometer for your melt, and also get a thermometer for your mold. Have a notebook right next to you when you cast and log the temps of your melt and mold and separate your bullets by when your temps fluctuate. Once you have the bullets sorted into batches by your temp fluctuations weigh the bullets and see where your sweet spot is. Aim for that goal. Some items may assist you with getting to that point like a PID controller for your lead pot. Also a hot plate for your mold. People have made PID controllers for hot plate/molds to get your mold at that precise temp and then try and maintain that temp throught your casting session with the alloy that is going into it.
BUT.......... I reccomend cast 'em and shoot 'em! If you want and overwhelming amount of knowledge on boolit casting come visit us over at www.castboolits.gunloads.com. You'll learn A LOT!

 

[dagger dog]

I cast that same boolit, with stick on wheel weights, they drop out at 412 to 414 grs.

 

[41 Mag]

As mentioned the alloy temp will make a big difference in your weights as will the mold getting hotter as you go along.

If you do not have one already you might check and see if NOE has one of the lead thermometers in stock, Lead Pot Thermometer

He has them priced well and is a great fellow to deal with.

As for the weights, your seeing the results of the above. As the aluminum heats up the cavity actually gets smaller. Depending on the alloy this will throw weights all over the place. There is a thermometer available to be inserted in some molds as well but it requires having a hole drilled in the end for the probe.When I first got started I picked one up but after about half a dozen times of using it I found that simply controlling the alloy worked just as good as long as I kept the cadence up with my pour rate.

With bigger bullets you don't have to run quite as fast to keep the mold hot. With one cavity molds using a pull pin for HP's or HB's you need to pour a bit faster to keep the pin hot or you will need to heat the pin in the alloy between pours to keep it hot.

My suggestion would be to pick up the thermometer, get your mold up to temp using either the casting pot to pre heat it or the alloy, get the alloy into the 675 - 700 degree range and start pouring. I would pour fast enough to get frosted looking bullets then alloy the mold to cool maybe 10 - 20 seconds and pour another. This should get you in the ball park for good bullets, Once you have the mold ht, and have a good pour you might set the old on a wet towel between pours just long enough to cool it a touch. Maybe a second or two at the most. This might help regulate the mold temp.

Casting is a balancing act where in some cases with some molds you can lean more to one side than with others. Once you hit a good middle ground you will find everything starting to balance out.

If your seriously into casting, and want to get as close as you can to repeatable temps with your alloy you should look into installing a PID controller ( Project PID ). This will allow you to set the temp you want to pour at, and the controller will hold it there within a few degrees one way or the other. Building it yourself might run you $100 for the parts and such depending on how thrifty you are at scrounging. I set up my Lee 4-20 with one after chasing the temp while pouring got to be a pain. Starting out with my alloy at say 685 and then once the level dropped it jumped up to 750 really quick. The PID will hold it where I want it down to the last drop.

When I started I found that my bullets varied in weight like yours, but after adding in the alloy thermometer to start with, and then the PID controller, I have found that my weights only vary by a few grains, and usually on a 10# batch less than 5-10 grains for the whole lot. I admit I might be a bit OCD about my bullets, but I use them for hunting and want each to be as close to the next. While it might not make a hill of beans to the end result on paper, in my mind while in the field I know I did everything I could to bring the best ammo I could assemble with me. With my shooting out to 50 - 100yds in some cases with my revolvers, I want all the added edge I can get.