Bullet casting math, nerds only

[redruns]

I have begun to process some lead for casting 9mm and 40s&w. This is a new adventure for me and there have been many things to figure out. One of the fun things was figuring out the return on investment. I have shared these notes in the hopes that someone can find value in them.

First I travelled near and far and collected some lead. Then reduced the raw supply to ingots.

- 156 ingots averaging 700 g made from range scrap = 109.2kg (240.2 lbs)
- 47 ingots averaging 768.8 g from $25 bucket of wheel weights 36.1kg (79.5lbs)
- Add lynotype alloy at a rate of 6:1 to range scrap. (made some assumptions about the RS composition)
- At 6:1 total lead supply = 240.2 + 240.2/6 + 79.5 = 360 lbs
- May need to source additional Sn. Hoping for up to 2% tin in range scrap
- Linotype = $6.00/lb +gst = $6.30/lb
- Wheel weights approx = $0.31/lb

a) total cost ($6.30/lb)(40lbs)+$25 = $277
b) cost per pound ($277/360lbs) = $0.769/lb
c) cost per 125 gn bullet ($0.769/lb)(125gr/bullet)/(7000gr/lb) = $0.0137/ 125 gr 9mm bullet
d) cost per 180gn bullet ($0.769/lb)(180gr/bullet)/(7000gr/lb) = $0.0198/ 180 gr 40 S&W bullet

Process of casting is to use two moulds, filling one while letting the other cool before dropping the bullets.
This should increase casting efficiency because there will be less time watching the mould waiting for it to cool enough to drop the bullets. Produce 9mm and 40 s&w at a ratio of 1:1, 6 at a time. We'll see if it works like planned.


360 lbs lead alloy
for every one 180 gr bullet there will be one 125 gr bullet
Determine the total number of 180 gr bullets and 125 gr bullets that can be produced from 360 lbs of lead alloy with a Lee 6 cavity mold.

360lbs = (x/2)(180gr+125gr)/7000gr/lb
x/2= (360lbs)(7000gr/lb)/(180gr+125gr)
x/2= 8262
360 lbs can produce 8262 180gr 40S&W bullets and 8262 125gr 9mm bullets

I'm certainly looking forward to shooting for 10 cents per round.

 

[Nova316]

Your math looks exactly like mine tho Linotype at $6 seems steep as I sold a bunch for $2.50/#
Using TG at 4gr/load you'll make each 9mm shot around 8 cents!
Though costing in lube or Powder coat will set you around you 10 cents. Still can shoot 3 for every 1 factory round

 

[Edenchef]

Why use two molds? Waiting to cool then heating up the mold again will not give you the best results. Typically the first few bullets go back into the pot anyway, because the mold doesn't fill out well, until it gets hot. Once you get the mold up to temp the cycle time is very short, the lead 'freezes' very fast. I drop mine onto an all cotton towel, a friend of mine drops his straight into a bucket of water. Save the cot of a second mold and get another caliber. JMHO.

 

[redruns]

Why use two molds? Waiting to cool then heating up the mold again will not give you the best results. Typically the first few bullets go back into the pot anyway, because the mold doesn't fill out well, until it gets hot. Once you get the mold up to temp the cycle time is very short, the lead 'freezes' very fast. I drop mine onto an all cotton towel, a friend of mine drops his straight into a bucket of water. Save the cot of a second mold and get another caliber. JMHO.

Yes, this is two different calibres at once, 40S&W and 9mm.

The two mould process may be more of a pain than I think, we'll see how it works out.

 

[Edenchef]

Yes, this is two different calibres at once, 40S&W and 9mm.

The two mould process may be more of a pain than I think, we'll see how it works out.

I have 6 different bullet molds, I only ever cast with one at a time, but often more than one during a run. With my Walker Conical, which is just single cavity, I can easily do 100 in an hour. With my 6 cavity, .45 ball mold; production is a bit faster.

 

[jamesharrison]

I think you got too complicated in your math.

360 pounds = 2,520,000 grains (=360x7000)
bullet weights 305 grs. (=180 + 125)
total production run = 8,262 of each (=2,520,000/305)
1,377 fills for each of your 6 gang moulds.

If it was me, I'd pre-heat both of your moulds, after correctly cleaning and prepping them, and use them both. Fill one, let sit full, then fill the other, then empty the first one, refill it and then empty the second one, refill it, then repeat until your furnace is empty, watching the temperature of your alloy.

I've never had to wait for my aluminum moulds to cool down. I cast with 5 or 6 (depending on bullet size) of my 12 moulds at a time using a production-line rotating system. Given that each mould is a 5-gang mould, my production rate is quite good for 4 hours work, using a Lee 20 pound melter. I water-quench my bullets in a 5 gallon pail and find there is no delay in production. By water-quenching mine, the w/w measures 28 BHN after 24 hours. Ten days doing 4 hours a day, I end up with around 1,000 of each of my 12 bullets after culling the bad ones, but by prepping my moulds and pre-heating them on a hot-plate, I find I have very low cull rates.

When I get a batch of metal to use, usually around 100 pounds or so, consiting of a bit of old solder, some range scrap, some old lead pipe and old-style truck tire weights, I melt it into ingots using old 12 cavity muffin tins found at the dump. This allows a rough cleaning of the metal. When I have several hundred pounds of ingots stored, I'll melt them all together, stir well and re-pour them into ingots, resulting in a homogenous batch of alloy. When I'm down to a hundred pounds or so, and have the next batch of ingots done up, I'll re-melt everything together and start again. By doing this, I don't find much difference in size or weight of my bullets.

 

[badd0g]

what kind of mold are you using? I use a lee 6 hole 230gr .45rn using 7-2 tin antimony mix I get from metalx in richmond and on a different table I have a pie plate with a wet terry rag in it after the mold is at the right temp I drop the bullets into a 5gal bucket and then run the bottom of the mold over the wet rag. it seems to keep it at the right temp for continuous casting it takes a while but you will recognize when the sprue looks right to determine the perfect temp. The ones pic took about 4hrs 42 lbs. finished Always wear glasses
Todd ps last time I paid 1.70 per lb for a 60 lb ingot

 

[jethunter]

... By water-quenching mine, the w/w measures 28 BHN after 24 hours.

That's interesting. The highest BHN I have ever been able get bullets made from ww is about 20-ish. That was from heat treating to over 400 degrees F for an hour and then dropping in ice water. Molds usually run about 350F or slightly under. Without the heat treating BHN has always been in the 12-14 range for the several thousand pounds of ww I melted down and tested before I started using commercial lead.