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Recipes

 Blending Cast Bullet Antimony Alloys

Table 1

Key to abbreviations Alloying with Roto Metals Super Hard

Table 2

Conversion Factors

By: Rick Kelter

Table 3

 

       Roto Metals, Inc. of San Leandro, CA has recently done a tremendous favor and service for bullet casters with the introduction of Roto Metals Super Hard Alloy. It is now a simple matter to blend (alloy) a limitless variety of lead/antimony alloys to suit your needs, it opens up a whole new world of possibilities for bullet alloys and bullet casters.

       Super Hard is a 70% lead (Pb), 30% antimony (Sb) alloy that is used to increase the antimony percentage (harden the alloy) of your current lead supply such as clip-on and stick-on (tape type) wheel weight, plumbers lead, sheet lead and many other lead alloys. It is made with virgin metals, not from scrap metals so you are adding perfectly "clean", new alloy to your casting pot. With the addition of pure bar tin from Roto Metals the sky is the limit and you take control of your casting alloys, even with many scrap lead alloys.

       Antimony (Sb). It is the current metal used to strengthen/harden lead alloys for bullet casters and for numerous applications in the metals industry. It is an extremely brittle metal but has unique characteristics in a lead alloy in addition to its basic hardening, such as the ability to heat treat a lead alloy bringing the final hardness up far more than what the percentage of antimony would suggest. Alloys such as monotype (19% Sb) and stereotype (23% Sb) are so brittle because of their extremely high Sb percentages, bullets cast of them can actually break in two by simply chambering a round or dropping it on a cement floor. Antimony is a valuable part of the bullet casters alloy but too much of a good thing is clearly not a good thing. Super Hard is for blending (alloying) with softer lead or lead alloys, never try to cast bullets with Super Hard alone, you will not be a happy camper.

       Antimony is a silver white metal, very hard and very brittle. It has no characteristic crystallographic surfaces when sheared. Melting temperature is 1167 F and even when melted at or above that temperature it is not easy to get a homogeneous alloy with lead. In addition, Sb in it's pure or powdered form is highly toxic and proper breathing apparatus and proper and thorough clean up afterwards is necessary. So what to do? Antimony is an important part of many bullet casting alloys but it's both difficult and could even be dangerous to try to alloy yourself. Here is one of the real services provided by Roto Metals, the professionals have done the difficult and dangerous part of alloying Pb/Sb for you. Super Hard melts at about 650o F, is homogeneous with your base alloy and thus blends in with your melt quickly and easily with your final flux before casting.

       Weight and Size differences. As the percentages of the alloys in a melt change other changes occur in addition to the weight of the bullet. In general the higher the percentage of Sb the larger the as cast diameter of the bullet and the larger the diameter of the bullet the more increase there is. In other words a 45 caliber bullet will show more of an increase than a .308" caliber bullet (table 3). In addition, the alloy percentages have a direct effect on the final sized diameter (table 1). I imagine the sizer die makers get daily phone calls from customers complaining (as an example) that their .309" die sizes to .3084" and not .309". If you change the alloy the weight, as cast diameter, shrinkage, sized diameter and BHN all change. Higher Sb percentages also result in less shrinkage as the bullet cools and it's possible for this simple fact to result in bullets that are a bit tougher to get to fall from the mold (table 2). From the tables it can also be seen that in reverse the softer the alloy (less Sb) and the larger the diameter of the bullet that more shrinkage will occur.

       Sb and Brittleness. As you have already read, raising the Sb percentage makes bullets brittle so the key is to not get carried away, your intended target should guide you to the maximum percent of Sb in an alloy. Look over the recipes I listed below and you'll notice that in only Hardball (6% Sb) and Lyman #2 (5% Sb) and 1 other (Alloy #2-1) did I go over 5% Sb and #2-1 is still under 5.5%. The vast majority of smokeless powder handgun and rifle loads should be well served with these Sb percentages. Hollow points intended for hunting/expansion should be about 2% Sb and 2% Sn. Thanks to Super Hard this is now fairly easy to dial in.

       The tin (Sn) in your melt. Sb oxidizes rapidly when in contact with air and the Sn in your melt helps inhibit this oxidation in melts up to about 750 degrees. With higher temps than this tin itself oxidizes much more rapidly and looses much of it's ability to inhibit Sb and Pb oxidation. It's not only the surface of the top of the melt in your pot that's in contact with air but also the stream of alloy from a bottom pour pot or even from a ladle that Sb will also oxidize, the hotter the alloy the faster the oxidation. This stream of alloy into your mold is where tin will play it's most effective roll in reducing the oxidation of Sb. By reducing the oxidation of both Sb/Pb tin reduces the surface tension of the melted alloy which enables your alloy to fill in the smallest corners and angles inside the mold resulting in well filled out bullets. The addition of 1 or 2% Sn is very beneficial when adding Sb to your alloy.

 
       The Base Metals. All clip-on wheel weight (CWW) recipes and percentages used in these recipes are based on the assumption that CWW has 2% Sb and 0.5% Sn plus a trace of arsenic (As). Additional tin in the below recipes added as pure bar tin. My batch of CWW (several batches blended together for a single uniform batch) with 2% Sn added tests 11-12 BHN.
 
       All stick-on (tape weights) (SWW) recipes and percentages used in these recipes are based on the assumption that SWW has 0% Sb and 0.5% Sn. SWW has no arsenic (As), it will HT with Sb added (Pb/Sb alloy) but not to the same extent as an Pb/Sb/As alloy. Additional tin in the below recipes added as pure bar tin. My batch of SWW (several batches blended together for a uniform single batch) tests 6 BHN.
 
       The percentages of WW alloy are assumptions because wheel weight alloy is scrap metal, there is no exact formula for making the weights and percentages vary not only from company to company but even from batch to batch within the same manufacturer as the price of and availability of raw materials change. By using these "assumed" percentages your alloy will be reasonably close to the below recipes even with some variability with your wheel weight alloy.
 
       All of the below recipes use either clip-on or stick-on wheel weight as the base metal. These recipes are but a minor sampling of what alloys Super Hard can be blended into, get out your wizards' cap and calculator and see what you can create to better suit your shooting needs. For the most part the below recipes were designed to allow me to experiment with final air cooled hardness, the aging time curve, as cast diameters, compare the differences and test to see what useful range 6 BHN SWW could be while keeping the Sb percentage reasonable.

 

Super Hard / WW Recipes

(Where no as cast weight or BHN given alloy not yet blended)

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Clip-on WW - Roto Metals Super Hard

 

Notes

Alloy 1   15 lb CWW / 1 lb Super Hard

Notes

Alloy 2  
     
Lead 107275 Gr.

92.75% Gr.

---

Lead

107275 Gr. 92.75%
Antimony 3904 Gr. 3.64% ---

Antimony

3904 Gr. 3.64%
Tin 4044 Gr. 3.77% (9.26 ounces) ---

Tin

1930 Gr. 1.8% (4.4 ounces)

Total weight

16.52 lb

BHN, Min 3 days  15

---

Total weight

16.225 lb

BHN, Min 3 days  12

         

 

Alloy 1-1

      Alloy 2-1  

15 lb CWW /

 

15 lb CWW / 2 lb Super Hard

Lead   % ---

Lead

112175 Gr. 92.65%
Antimony   % ---

Antimony

6004 Gr. 5.35%
Tin   % ( ounces) ---

Tin

4206.5 Gr. 2%  (5.1 ounces)

Total weight

 lb

BHN, Min  days

---

Total weight  17.48 lb

BHN, Min 3 days  13

Alloy #1 cast with Lyman #311672 @ 160.0 Gr. (average weight) and air cooled tested 14 BHN with the LBT BHN tester on the second day after casting - 15 BHN on day 3 - 15 BHN on day 4 - 15 BHN on day 5.  
Alloy #2 cast with Lyman #311672 @ 161.0 Gr. (average weight) and air cooled tested 11 BHN with the LBT BHN tester on the second day after casting - 12 BHN on day 3. The only difference between #1 & #2 is the Sn percentage. Does additional Sn harden the alloy? It appears so and testing this was the purpose of making #2 identical to #1 except the Sn percentage.
Alloy #2-1 cast with Lyman #311672 @ 159.3.0 Gr. (average weight) and air cooled tested 13 BHN with the LBT BHN tester on the second day after casting, in 2 weeks it remained 13 BHN, in 30 days it reached 14 BHN. Alloy #2-1 was made by adding 1 pound SH and 313 Gr. Sn to alloy #2, the Sn added to bring the Sn % up to 2%.
Sn % added to Pb weight. Sb % added to Pb weight.
Trace of (As) from CWW in the above alloys. A trace of As is all that's needed for dramatic HT results with a Pb/Sb alloy.
1 lb CWW = 6825 Gr Pb, about 140 Gr Sb and 35 Gr Sn - 1 lb SH = 4900 Gr Pb, 2100 Gr Sb.

 

Stick-on WW - Roto Metals Super Hard

 

Notes

Alloy 3   15 lb SWW / 2 lb Super Hard

Notes

Alloy 4

           
Lead 114275 Gr.

92.6%

---

Lead

114275 Gr. 94.51%
Antimony 4182 Gr. 3.66% ---

Antimony

4182 Gr. 3.66%
Tin 4056 Gr. 3.55% (9.3 ounces) ---

Tin

2022 Gr. 1.77% (4.6 ounces)  

Total weight

17.5 lb

BHN, Min  days 

---

Total weight

17.2 lb

BHN, Min  days 

Sn % added to Pb weight. Sb % added to Pb weight.
1 lb SWW = 6965 Gr Pb and 35 Gr Sn - 1 lb SH = 4900 Gr Pb, 2100 Gr Sb.

 

Stick-on WW - Roto Metals Super Hard

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Notes

Alloy 5

15 lb SWW / 1 & 1.5 lb Super Hard

Notes

Alloy 6

     
*1 Pound Super Hard  

1.5 Pound Super Hard

Lead 109375 Gr. 96.3% ---

Lead

111825 Gr. 95.1%
Antimony 2012 Gr. 1.84% ---

Antimony

3153 Gr. 2.82%
Tin 2056 Gr. 1.88% (4.7 ounces) ---

Tin

2180 Gr. 1.95% (5.0 ounces)

Total weight

16.25 lb

BHN, Min  days 

---

Total weight

16.75 lb

BHN, Min 2 days  11

*This recipe is close to straight CWW Pb/Sb percentage with about 1.5% added tin (no As when using SWW)
Alloy #6 cast with Lyman #311672 @ 162.5 Gr. (average weight) and air cooled tested 11 BHN with the LBT BHN tester in 24 hours after casting.
Sn % added to Pb weight. Sb % added to Pb weight.
1 lb SWW = 6965 Gr Pb, 35 Gr Sn / 1 lb SH = 4900 Gr Pb, 2100 Gr Sb.

 

Stick-on WW - Roto Metals Super Hard

 

Notes

Alloy 7

15 lb SWW   w/ 2 & 2.5 lb Super Hard

Notes

Alloy 8

     

2 Pounds Super Hard

    2.5 Pounds Super Hard
Lead 114275 Gr.

94.32%

---

Lead

117775 Gr. 93.55%
Antimony 4205 Gr. 3.68% ---

Antimony

5241 Gr. 4.45%
Tin 2285.5 Gr. 2% (5.2 ounces) ---

Tin

2355 Gr. 2.0% (5.4 ounces)

Total weight

17.25 lb

BHN, Min 2 days  12

---

Total weight

17.9 lb

BHN, Min 2 days  13

Alloy #7 cast with Lyman #311672 @ 161.5 Gr. (average weight) and air cooled tested 12 BHN with the LBT BHN tester 3 days after casting.
Alloy #8 cast with Lyman #311672 @ 161.0 Gr. (average weight) and air cooled tested 13 BHN with the LBT BHN tester 2 days after casting. Alloy #8 was made by adding 1/2 pound and 69.5 Gr. Sn (to keep the Sn percentage at 2%) to alloy #7.

1 lb SWW = 6965 Gr Pb and 35 Gr Sn / 1 lb SH = 4900 Gr Pb, 2100 Gr Sb.

Sn % added to Pb weight. Sb % added to Pb weight.

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Alloy 9

Hardball From 6 BHN SWW  

Alloy 10

Lyman #2 From 6 BHN SWW

Notes

15 lb SWW / 3.45 lb Super Hard  

Notes

15 lb SWW / 3 lb Super Hard

 

     

 

   
Lead 121380 Gr. 92%

 

---

Lead

125475 Gr.

90%
Antimony 7282 Gr. 6% ---

Antimony

6273.75 Gr. 5%
Tin 2427 Gr. 2% (5.5 ounces) ---

Tin

6273.75 Gr.

5%  (14.3 ounces)

Total weight

18.75 lb

BHN, Min 2 days

12

---

Total weight

19.72 lb

  BHN, Min  days

Alloy #9 cast with Lyman #311672 @ 161.0 Gr. (average weight) and 12 BHN in 48 hours.
1 lb SWW = 6965 Gr Pb and 35 Gr Sn / 1 lb SH = 4900 Gr Pb, 2100 Gr Sb.
Sn % added to Pb weight. Sb % added to Pb weight.

 

Notes, conclusions & surprises

Notes & conclusions on alloys 1 and 2: < Go to alloys 1 & 2 >
Alloys #1 & #2, blended from the same lot of clip-on WW, the only difference is the percentage of added tin with alloy #1 having 3.77% and alloy #2 having 1.8% and yet there is marked difference in age hardening. In fact alloy #2 BHN in two days is basically the same BHN as the base metal even though 1 pound of Super Hard was added to 15 pounds CWW doubling the amount of Sb.

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Notes & conclusions on alloys 3 and 4: < Go to alloys 3 & 4 >

Neither alloy blended as of this writing.
 
Notes & conclusions on alloys 5 and 6: < Go to alloys 5 & 6 >
Alloy #5 not yet blended.
Alloy #6 took 6 BHN SWW to 11 BHN in 2 days, basically air cooled CWW BHN.
 
Notes & conclusions on alloys 7 and 8: < Go to alloys 7 & 8 >
Alloy #8 was blended by adding 0.5 pound Super Hard and enough Sn to keep the percentage at 2% to alloy #7. The modest gain over alloy #7 in BHN for alloy #8 is not an economical use of the Super Hard.
 
Notes & conclusions on alloy 9: < Go to alloy 9 >
Got SWW or other soft lead alloy? With Super Hard you can turn your soft alloy into Hardball at far less cost than purchasing hardball alloy. Using round numbers and the costs of Hardball vs. the cost of Super Hard and tin at the prices as of this writing the cost to make your own is less than $0.80 per pound for the nearly 19 pounds in the recipe. Hardball is currently on sale at Roto Metals for $2.02 per pound plus shipping. At Midway USA hardball is $3.78 per pound.
 
Notes & conclusions on alloy 10: < Go to alloy 10 >
The 20 pounds of Lyman #2 in the recipe will cost about $22.00 to make ($1.10 per pound) assuming you already have the soft lead. By contrast Roto Metals (as of this writing) has Lyman #2 on sale @ $2.32 per pound, the regular price is $2.73 per pound with free shipping if your order is over $100.00, Midway USA does not list Lyman #2.

 

(Table 1)   Bullet alloy as-cast & final dia. w/.308 sizing die

 

 

Wheel

 

 

 

Lead

Weights

Lyman #2

Linotype

As-cast dia.

.309"

.3095"

.310"

.3104"

Sized dia.

.3078"

.3079"

.3084"

.3084"

 

(table 2)

Alloy shrinkage of cast bullets    

(table 3)

Composition, %     Shrinkage  

Shrinkage - Bullet Diameter, Inches

Type of alloy

Tin

Antimony Lead BHN Linear, %   Alloy .308 .357 .452
Linotype 4 12 84 18 .65   Linotype .002 .0025 .003
Monotype 9 19 72 26 .65   Lyman # 2 .0025 .0025 .0035
Antimony -- 100 -- 50 .47   Soft Lead .0035 .004 .005
Lead -- -- 100 5 1.13          
Tin 100 -- -- 7 .90    

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Key to symbols/abbreviations used in this article
Metal Symbol

Abbreviations

Lead Pb

CWW

Clip-on Wheel Weight (w/2% Sn 11-12 BHN)
Antimony Sb

SWW

Stick-on Wheel Weight (Tape Weights) (Straight SWW 6 BHN)
Tin Sn

WW

Wheel Weight
Arsenic As

SH

Super Hard Alloy (Roto Metals)
   

lb

Pounds
   

BHN

Brinell Hardness Number
   

HT

Heat Treat, quenching from the mold or oven heat treating
   

Gr.

Grains, (7,000 Gr. = 1pound)
     
Conversion factors:
To convert grains to ounces multiply grains by .00229, example from alloy #1 above, 4044 Gr Sn X .00229 = 9.26 ounces. (rounded off to nearest 100th of an ounce).
 
To convert ounces to grains multiply ounces by 437.5, example from alloy #1, 9.26 ounces Sn x 437.5 = 4051 Gr (rounded off to nearest 100th of an ounce).

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Roto Metals Super Hard = 70% Pb - 30% Sb / 1lb Super Hard = 4900 Gr Pb / 2100 Gr Sb.

Roto Metals bar tin = 99.9% Pure
 
Note: You could create the above alloy recipes by converting to ounces rather than grains, however, there are 16 ounces to a pound and 7000 Gr to a pound, any rounding off or minor errors using ounces would create fairly large variations in pot to pot alloy percentages (consistency). A 10% error (or rounding off) with grains is a 70 Gr variation for the entire pot of alloy. A 10% error using ounces is 1.6 ounces or 700 Gr. By converting to grains and rounding off to hundreds of an ounce such variations are statistically irrelevant.
 

There is only one place you can order Super Hard

 
 

http://www.rotometals.com

800-779-1102

$100.00+ orders qualify for free shipping

 

 
 
 
Warning: All technical data mentioned, especially handloading and bullet casting, reflect the limited experience of individuals using specific tools, products, equipment and components under specific conditions and circumstances not necessarily reported in the article or on this web site and over which The Los Angeles Silhouette Club (LASC), this web site or the author has no control. The above has no control over the condition of your firearms or your methods, components, tools, techniques or circumstances and disclaims all and any responsibility for any person using any data mentioned. Always consult recognized reloading manuals.