Variations in cast bullets

[gmww]

In preperation for an up coming hunt, I've been casting Great Plains and Minie ball bullets from Lyman molds. This is for my fast twist .54. I've notices variations in the final cast bullets. Not so much in the Great Plains but more with the Minie ball mold.

The first thing I noticed was they don't cast 425 grns as the box says it would. They are ranging from 380's to 405 grns. Mostly in the 390's.

At first I thought I got my lead supply mixed up and was casting hard cast. I checked and these are my soft lead supply. My thumb nail easily scratched the lead. Any thoughts? :hmm:

 

[ohio ramrod]

That much variation sounds like air pockets, or mold not completely closed. Have tou mic'ed the diameters?

 

[gmww]

Not yet. The big difference is Minie ball has an aluminum piece in the middle to create the cavity at the base. I have noticed that casting differs from when the lead it high in the Lee Melting pot vs in the middle vs near the bottom.

 

[mooman76]

That is allot of variation. You have some inconsistancies there. When the pot gets lower you have less pressure and that could be part of it. Like stated you probably aren't getting good fill out or an air gap. Keep the pot filled better and see if that helps. It is common for moulds not to drop as stated but usually just a small difference because a variables. Keep dropping bullets and you will get more consistant.

 

[gmww]

Thanks guys. I might go to a cast iron pot for melting lead and a ladle. I usually use this for my hard cast stuff. I'll see what happens. Right now about half are in the 390s. A little more that 1/4 is over 400 and the rest is 380s.

 

[mooman76]

Some people find that when casting the larger grained bullets they do better ladle pouring.

 

[gmww]

The odd thing is my Great Plains mold seems to be pretty accurate from the Lee Pot.

I tried one more thing with the Lee Pot just now. I lowered the Temp since I was already at Hi. I went to #7. I also mated the mold with the Lee Pot during the pour and after a second lowered it to see when to stop. It made for some very clean sharp bullets. It has cast a higher ratio of 390's and smaller ratio of all others. I'm seeing two groups showing up. 405 gr. and 395 grns.

 

[jamesthomas]

I use a lee pot made for ladle casting. I have found that using a ladle gives me more of a consistant cast. Perhaps your mold is marked wrong? 395 to 405 seems way to light for a mold marked 425 even if you get a air pocket. :idunno:

 

[gmww]

Upon closer inspection of the mold, it appears I might be able to adjust the depth of the cavity thus giving me more volume to pour lead into.

Never seen this kind of mold before. I'll have to do more experimenting.

 

[nkbj]

Please if you would, show us some pictures if you get the time.

 

[Idaho Ron]

You might have an adjustable mould, but if it is the Lyman Plains bullet I don't think it is. I think the problem is alloy in the lead. without a hardness tester you don't know. I can scratch lead that is 18BHn with my thumb. You can either buy a batch of pure from Rotometal or you can send me three bullets and I will test them for you I would be happy to do it. If you buy the lead from Rotometal you know it is pure. Ron

 

[gmww]

The Lyman is a simple mold. The Minie ball is a whole different story. I'll post a photo in a moment. Got to go into the garage and get it.

 

[gmww]

 

[Idaho Ron]

I think that mould could be made to be adjustable to make them smaller but in my opinion it was not intended to be adjustable. Here is my adjustable North South Skirmish mould. The bolt that runs up and down needed a lock nut. I added that and contacted RCBS. They are now adding a lock nut to all of these moulds. Any way I can see how you might think yours is adjustable, and it could easily be made adjustable I think. Here is my mould and what the bullets look like. yours would need smooth sides to be adjustable I think. Ron

 

[gmww]

Thanks, I'm going to see if this will produce a 425grn as published with it lowered. I'm going to add lock washers like yours. I hope to give it a try this weekend.

 

[Idaho Ron]

Thanks, I'm going to see if this will produce a 425grn as published with it lowered. I'm going to add lock washers like yours. I hope to give it a try this weekend.

I actually used a lock nut on mine. Let us know how it goes. Ron

 

[gmww]

I will.

 

[Billnpatti]

I am inclined to think that it the two main problems are the change in head pressure as the pot empties and a possible variation in the alloy. If your lead is not absolutely pure, the other lighter metals in your alloy will tend to float to the top when the lead melts. As your pot empties, not only does your head pressure decrease, you start getting more and more of the lighter metals. This all assumes that your technique is good and you are making sure that your mould is good and hot when you are casting. If you have to stop to take a pee break or answer the phone, your mould can cool and start throwing poorly formed bullets until it heats up sufficiently again. To see if your alloy is changing as your pot empties, set aside some bullets from the first of your run when the pot is full and several when your pot gets low. When they cool to room temperature, use a good micrometer to measure their diameter. If the diameter changes, this is most likely due to a difference in alloy because different alloys have different thermal expansion coefficients and will throw bullets of differing diameters. If you find this to be the case, it just means that you will have to keep your pot full and will need to flux more often to keep the alloys mixed and consistant and to keep your head pressure more consistant.

 

[Dphar]

Thanks guys. I might go to a cast iron pot for melting lead and a ladle. I usually use this for my hard cast stuff. I'll see what happens. Right now about half are in the 390s. A little more that 1/4 is over 400 and the rest is 380s.

To pour uniform bullet weights...
First you need a GOOD electric pot that will hold the temperature closely. If it varies too much the weight will too. If its impossible to get uniform bullets buy a lead thermometer and see what temp you are REALLY casting at.
Then you need a GOOD hot mould that is properly vented so as to fill proplerly. Many moulds need the vent lines deburred.
Smoking may also be needed at least at the start of a run it insulates the molten metal and slows the cooling just a little.
Then you need a consistent pouring routine and speed.
If you stop casting for more than a couple of minutes the bullets must be considered a separate lot for weighing. When casting I cast till the pot is empty only adding the hot sprues back to the pot. When its empty I refill and give it time to melt and normalize.
Minie bullets with the base plug etc. Good luck. The complexity of the mold works against the caster.
Use a ladle its far more consistent than the bottom poor pots.
Pure lead needs a higher pour temp than lead:tin alloys do. Even 40:1 flows far better than pure lead due to a lower melt temp.
I would think that 40:1 would work for Minies, its very close to pure lead in hardness, but I don't shoot them so have never tried it.
Dan

 

[ian45662]

Where did you get your mold?