Over weight Cast Bullet powder charges?

fiddler

fiddler

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I'm enjoying making cast bullets lately. Its new to me, learning a lot, and yah, its a rabbit hole.


I'm finding my cast bullets to be over weight by 3-7 %


Is there a rule of thumb to recalculate known powder charges (Loading manual charts) for when the bullets are heavier by 5, 10, 14 grains ?





Ex.

38-55 bullets 250gr are scaling out at 258grains

45cal 200 grains are weighing 214grains


and

358 cal 125gr are weighing in at 130grains.
 
I don't have the answer to your question regarding powder but it sounds to me that your lead alloy is a bit too pure.
You could alloy your casting lead with some more tin and or antimony so the weight of your dropped bullet goes down.
 
i cast for all my guns and it all depends on the lead alloy you are using. the overweight is normal from my casting but I stay under the max loading to make sure I do not have a problem. if you want to get your bullets to shoot really tight groups weigh the bullets in weight groups example 129.0-129.9. it is a bit of work but worth it in the long run.
 
you have to work up a load for each Bullet / for each gun

5-10g is not excessive ... So much of the cast bullet load data published will state what the bullet weight is/ was

you will find the weight difference is not a problem if you are loading target loads, or even accurate top loads used for hunting

You will get more of a velocity change from summer loads to winter loads and vice versa
 
It could be your scale, and an overcut 45. Your mold maker should indicate which alloy they use for their weights, and variations depending on alloy.

But by any means, work your loads up. Best accuracy seldom comes at max loads.
 
mg34 said:
i cast for all my guns and it all depends on the lead alloy you are using. the overweight is normal from my casting but I stay under the max loading to make sure I do not have a problem. if you want to get your bullets to shoot really tight groups weigh the bullets in weight groups example 129.0-129.9. it is a bit of work but worth it in the long run.
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Most of the bullets that came out good from the mold are all within 1 grain of each other. Very consistent, just 8 gr heavier than the specified 250gr mold
 
Since you are consistently getting higher than estimated bullet weights out of a variety of moulds it's pretty much a guarantee that your bullet alloy needs a little less lead and more tin/antimony. Drop your powder charges by at least the percentage your bullets are overweight e.g. if the bullet is 7% overweight drop the powder charge weight by at least 7%. In fact I would go to 10% just for an increased margin of safety.
 
ted_dent said:
Since you are consistently getting higher than estimated bullet weights out of a variety of moulds it's pretty much a guarantee that your bullet alloy needs a little less lead and more tin/antimony. Drop your powder charges by at least the percentage your bullets are overweight e.g. if the bullet is 7% overweight drop the powder charge weight by at least 7%. In fact I would go to 10% just for an increased margin of safety.
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I had another guy tell me the same thing, but your only the second person to say that.

I've considered the alloy percentage but I hope to work with it because I have an un-exhaustible supply of clean ingots for person use.
 
I shoot extensively lead bullet in , 30-30, 45-70, 45-75, 45-60, GC and no GC, and never bothered with bullet weight variation. Got a 405 mould that drop at 425.

Load is developed for 425, and there is no powder reducing to do, since you should always start with a lower powder charge than max with your new bullet and work the load up. Thats the way to find an accurate load..same as the copper bullet load development.

Never heard of bullet weight over 7%, start 7 % lower.
Starting 10% below max powder charge will take care of bullet weight -mold -alloy variation. No need for voodoo or magic.


Got close to 40 moulds here..custom and commercial, and none is exactly on the money as per the advertised weight. They are 99% overweight. And yes, my custom mould are made for specifics alloys.
 
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fiddler said:
I had another guy tell me the same thing, but your only the second person to say that.

I've considered the alloy percentage but I hope to work with it because I have an un-exhaustible supply of clean ingots for person use.
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Sorry, let me clarify as my original post could be misinterpreted. If the max charge is 10 gr. you would normally drop back at least 10% for a starting charge so 10 gr. - 10% = 9 gr. However, if the bullets are 7% heavier than what the loading data says then you would further reduce the charge by another 7% so 9 gr. x 7% = .6 grains which gives a final charge weight of 8.4 grains (10 gr. - 1 gr. - .6 gr.).

This is not a scientific formula but what is does is provide you with a simple method of making sure you have reduced the powder charge sufficiently so that a higher than posted bullet weight is not going to push you into dangerous pressure territory.

Obviously I wouldn't suggest reducing the start charge weight by only 7% when loading manuals say 10% (and with a lighter bullet).

I apologize for the confusion.
 
ted_dent said:
Sorry, let me clarify as my original post could be misinterpreted. If the max charge is 10 gr. you would normally drop back at least 10% for a starting charge so 10 gr. - 10% = 9 gr. However, if the bullets are 7% heavier than what the loading data says then you would further reduce the charge by another 7% so 9 gr. x 7% = .6 grains which gives a final charge weight of 8.4 grains (10 gr. - 1 gr. - .6 gr.).

This is not a scientific formula but what is does is provide you with a simple method of making sure you have reduced the powder charge sufficiently so that a higher than posted bullet weight is not going to push you into dangerous pressure territory.

Obviously I wouldn't suggest reducing the start charge weight by only 7% when loading manuals say 10% (and with a lighter bullet).

I apologize for the confusion.
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Its all good. I take in and consider all information. The best information is from the guys who've done it.
 
Janeau said:
I shoot extensively lead bullet in , 30-30, 45-70, 45-75, 45-60, GC and no GC, and never bothered with bullet weight variation. Got a 405 mould that drop at 425.

Load is developed for 425, and there is no powder reducing to do, since you should always start with a lower powder charge than max with your new bullet and work the load up. Thats the way to find an accurate load..same as the copper bullet load development.

Never heard of bullet weight over 7%, start 7 % lower.
Starting 10% below max powder charge will take care of bullet weight -mold -alloy variation. No need for voodoo or magic.


Got close to 40 moulds here..custom and commercial, and none is exactly on the money as per the advertised weight. They are 99% overweight. And yes, my custom mould are made for specifics alloys.
Click to expand...



This is what they were getting at, staying below the max pressure charge. The low charge stays the same.

If I look at charge tables for .357 for example from an old Lyman book, cast bullets from 120gr all the way up to 195gr, the start charge is 4.0gr of Unique for ALL LOADS. But backs off the max powder charge as the cast bullet gets heavier.
 
Call me nuts (and maybe I’n not alone in this boat) but sometimes I pop my casts into a drill chuck (lightly tightened) and lean the tail end onto a file to clean up the sprue and get them all weighing the same.
 
Not unusual for a mold to make bullets several grains heavier or lighter than nominal.

If your load data is at max for 250gr, you'd need to back off some for a heavier bullet. But most cast bullet data is already quite mild, so using the same powder charge would be ok in that case.
 
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