Tuesday, June 06, 2023

Once upon a time someone took pity and provided a formula (updated)

to convert some other alloys to 20-1.  I cannot find the post to ask the individual, so in a blanket request, does anyone know what the formula would be for lead to add to change 20-1 to 30-1?

I've been trying to work it out, but my brain won't seem to grasp numbers right now.

Added: Thanks to all for the data.  Reason asked is I tried some .45-70 loads using 30-1 instead of 20-1, and the rifle seemed to like the change.
And yes, there will be further testing before I start converting a bunch of stuff to the different alloy.


Matthew said...

I have a pencil here, let's see. Got it! For every 21 parts of 20:1, add 10 parts of the same stuff you already have 20 of. Boom, 30:1. Works for any consistent units, grains, ounces, gallons, tons, train loads etc. It's just a ratio.

Anonymous said...

Assuming you have 21grams of lead alloy where 20:1 is the lead to alloy ratio. Then you need to add 10 more grams of lead to the mix.


Anonymous said...

As Matthew said it's just a ratio.

First the hard way. Weigh the 20-1 lead you have and divide by 21. The result is the weight of tin in the alloy. Multiply that by 10 and add that weight in pure lead, melt it all together and you'll have 30-1.

Example - you have 14lbs of 20-1.

14 x 16 = 224oz

224/21 = 10.66oz

so you have 10.66oz of Tin and 213.33 of Lead in your 20-1

10 x 10.66 = 106.66oz or 6.66lbs of Lead to be added. (To make 40-1 add double, to make 25-1 add half)

224 + 106.66 = 330.66 Final weight of alloy batch.

Alloy weight 330.66 divided by Tin weight of 10.66 equals 31.01

Quick and dirty, weigh the 20-1 alloy multiply by .5, add that weight in Lead and you will have a 30.5 to 1 ratio, which is close enough for government work. If you want to be more accurate multiply by .477 and you will a 30.01 to 1 ratio.


Bob W said...

I was trying to put an image of a spreadsheet to calculate the additional weight of lead. I tried an image tag but it did not work but I am not an HTML user. Would the spreadsheet be useful?

20/21 * Weight of original mix to adjust = weight of lead in original mix
weight of lead in original mix * 30/20 = Weight of lead in new mix
Weight of lead in new mix - weight of lead in original mix = weight of lead to add

1/21 * Weight of original mix to adjust = weight of alloy in original mix

Weight of lead in new mix / weight of alloy in original mix = New ratio (as a check)

Firehand said...

Bob, I think that covers it.

And thank you, everyone

taminator013 said...

Shame on you for losing my coversion formulae.....

Firehand said...

Now I remember it was you!
I've still got those. But trying to reverse to make 20-1 to 30-1, my mind was having trouble with.