What is 25 to 1 Alloy in %Tin (4 or 3.85)?

[Defcon-One]

I have been looking at Rotometals website and they have 25 to 1 alloy that is supposed to be 4% Tin. They say it is 25 parts Lead, 1 part Tin.

Based on that, it should be 1/25+1 = 1/26 = 3.85% Tin

So, one is right, the other is wrong. Is 25 to 1 alloy, as we use it here in bullet land, 4% Tin (24 parts Lead to 1 part Tin) or is it 3.85% Tin (25 parts Lead to 1 Part Tin).

Bumpos calculator say 4% Tin for 25 to 1 up at the top, but if you mix 25 lbs. of pure Lead with 1 lb. of pure Tin (25:1) it says 3.85% Tin?

Which is it?

If you KNOW, please post here! I am getting dizzy.....I say Rotometals is wrong and 25 to 1 is 3.85% Tin. Who agrees or disagrees and why.

[fredj338]

Close enough for casting. You aren't making guided missiles.

[four70nitro]

Think of it as 1 part in 25 so that the tin is 1/25 of the mixture or 4%.

I never heard of anyone dividing by 26 - I know they say 1-to-25 mixture, but what they mean is 1 part in 25.

[white eagle]

1 2 25 = 25 2 1

[Doc Highwall]

When they sat 25:1 they mean 25 lbs. of lead and 1 lb. of tin for a total weight of 26 lbs..

30:1 is 30 lbs. lead 1 lb. tin =31 lbs..

If you want to know the percentages of tin divide 1 by the ratio you want.

1/20= .05%
1/25= .04%
1/30= .033%

[Defcon-One]

Doc:

I got it, but it is:

1/(20+1) * 100 = 4.80%
1/(25+1) * 100 = 3.85%
1/(30+1) * 100 = 3.20%

Isn't it?

The amount of Tin divided by the Total Amount times 100 for percent!

[btroj]

I would call it 3.85%. It is 1 part tin in 26 parts of total alloy.

[Defcon-One]

Thanks btroj, you win!

I got smart and had a friend check in his Lyman manual for me. The answer is in fact 3.85% Tin for 25 to 1 alloy, not 4% Tin.

That is according to Lyman 4th Edition, Cast Bullet Handbook.

They say that 10 to 1 is 9% Tin (1/11 * 100 = 9.0%)
and 20 to 1 is 4.8% Tin (1/21 * 100 = 4.76%. They rounded up to 4.8%)

Based on that, my math was correct and 25 to 1 is 3.85% Tin. (1/(25 + 1) * 100 = 3.85%)

Also, going in another direction I found a quote from a Glen Fryxell article on bullet metals:

Glen wrote, “… For hollow point bullets I have grown fond of using 25-to-1 alloy (6 lbs pure lead with ½ lb. of 50/50 solder)…..”

The math on that shows Glen’s 25 to 1 recipe to be 3.85% Tin as well.

Live and Learn! Learn to trust what you know!

So, Rotometals 25 to 1 is not the classic 25 to 1 alloy of old, it is actually 24 parts Lead to 1 part Tin, with 4% Tin!

[Doc Highwall]

Defcon-One, when you make 20:1 ratio, means 20 Lbs. lead and 1 Lb. tin for a total of 21 Lbs. The ratio is 20:1
1/20 = .05%
20 Lbs. lead x .05% tin =1 Lb. for a total weight of 21 Lbs.

[Defcon-One]

Doc:

Your saying that the Tin content in 20:1 by weight is 5% of the Lead content. OK, I get that!

So, it follows that the Tin content in 25:1 by weight is 4% of the Lead content.

But the percentage of Tin in the actual mix, (25 parts Lead to 1 part Tin) is really 3.85% and there is 96.15% Lead. That is what matters to me and apparently to Lyman and Glen Fryxell as well.

That is consistent with what I was saying all along!

It is not what Rotometals is doing:


Twenty five parts of lead and one part of tin (96% lead, 4% tin).

and it is not what Bumpo's calculator says up top!

[Stick_man]

Defcon actually has it correct. In a 25:1 alloy, the 1 part would be 4% of the weight of the 25 part. However, that 1 part is only 3.85% of the total combined alloy weight. In my experience, you can find a .15% difference in tin content in common clip-on wheel weights. If you weigh 1000 200gr. boolits together, you might find a difference of maybe 1/2 pound in total weight.

[Gtek]

You must sit very still and be very quiet, you can hear the engineers rustling around over there. I love this place! Gtek

[bumpo628]

My calculator will have the updated formulas on the next release.
Thanks for chasing down a source of reliable information.

[btroj]

I suppose the real question is what does 20:1 mean.

Is it 1 part in 20

Or 1 part to 20 parts

Being that itis referred to as 20 to 1 I would say it is just that 20 parts lead to 1 part tin. Hence it contains 21 parts, not 20.

I don't think the difference is enough to be relevant but it does show that anything left open to interpretation can cause confusion. If it was just called 4 percent tin in lead we would know exactly what we were talking about.

[Orochimaru]

According to my recollection (which is in agreement with Wikipedia) a ratio of 20:1 means 20 parts of lead to 1 part of tin.

Quoth the wiki:


If a mixture contains substances A, B, C & D in the ratio 5:9:4:2 then there are 5 parts of A for every 9 parts of B, 4 parts of C and 2 parts of D. As 5+9+4+2=20, the total mixture contains 5/20 of A (5 parts out of 20), 9/20 of B, 4/20 of C, and 2/20 of D. If we divide all numbers by the total and multiply by 100, this is converted to percentages: 25% A, 45% B, 20% C, and 10% D (equivalent to writing the ratio as 25:45:20:10).

So the percentage would be 1/21, or about 4.8%

[lwknight]

OK, here is the scoop.
Rotometals owner , Ryan himself told his sales clerk that the 25 to 1 is truly 4% tin and it is called 25 to 1 because that is what people generally look for when they really mean 4% tin.

[Defcon-One]

This thread was started by me to confirm the rules of metals nomenclature where ratios are concerned.

It should in no way effect your opinion of Rotometals.

They are a top-notch company and their products and customer service are exceptional. If you want to buy a known alloy of certified content, I would argue that there is no better place to buy it than Rotometals.

They are friendly to our craft! What would we do without products like their Super Hard?

[Doc Highwall]

OK after all this can we see the difference on the target? :lol:

I love this forum when a lot of different views come out and nobody gets made or upset.

I look at it as ratios like it is written in the manuals for my answer, but I also see from the other view point that their answer is also correct.

[darkroommike]

In my own notebooks, (and I also do darkroom work) I use 1+25 nomenclature for a dilution and 1:25 for a ratio. The first is one part plus twenty five parts, the second is one in 25 parts.

[Defcon-One]

This was my favorite comment:


You must sit very still and be very quiet, you can hear the engineers rustling around over there. I love this place! Gtek

I am an Engineer by education with 15 years in manufacturing before moving on. I mean it is obvious, who else would really care about 0.15%?

I'll work on the target thing if the weather ever cools down. It is 99 derees F and 99% humidity today! I can hardly breath the air is so thick!

[Gtek]

Glad you liked it, I grew up with one and called him DAD! Gtek