Alloy question???

[GunsAndHarley]

I read a lot about casting lately as I will start casting my own bullets prety soon.
One thing I see often about alloy is a ratio, like 30:1 or 20:1. Could anybody explain what is this ratio? I am guessing lead to tin but not realy positive about that.

I want to cast some 45-70 405gr and thinking using #2 alloy at about 1800 fps. I read all I could find in casting and alloy choice is the hardest part for me, so many opinions to screw my mind and I dont even speak of gc vs on gc...

Thanks

[jmort]

20 pounds of lead and one pound of tin, etc. #2 is a great alloy, but expensive due to high tin content. Spend some more time studying the link at the bottom of the forum page. Lot of good/great alloy information.
http://www.lasc.us/CastBulletNotes.htm

[Mitch]

here is a site that has some info http://www.rotometals.com/Bullet-Casting-Alloys-s/5.htm

[John Boy]

Lyman "Cast Bullet Handbook: 4th Edition"


http://www.midwayusa.com/product/867465/lyman-cast-bullet-handbook-4th-edition-book

[bumpo628]

Lead-Tin alloy ratios like 30:1 mean 30 parts lead mixed with 1 part tin.
Ex.: 30 lbs of lead plus 1 lb of tin mixed in the pot.
That means there are a total of 31 parts in the mix.
1:30 gives you a tin % = 1/(30+1) = 3.23% tin (not 1/30 = 3.33%)

The difference in how it is calculated is not very significant at that small of a ratio.
However, it increases as the ratio gets closer together. For example:
1:10 gives you a tin % = 1/(1+10) = 9.09% tin (not 1/10 = 10%)
1:2 gives you a tin % = 1/(1+2) = 33.3% tin (not 1/2 = 50%)