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Test the assertion:

Bullets cast of alloys with antimony expand as they age.

Do cast bullets expand as they age? Short term test - days 0 to 8.

 



 

Experiment 110515-A

Background:

It seems to be accepted dogma that you must not size or load cast bullets for some ( always unspecified ) time period after they are cast because they will expand as they age and thereby be too large to chamber of perhaps to fire safely.

Since I have been casting and loading cast bullets in handguns and rifles since 1956, I immediately rolled my eyes and thought "Oh No. another one of those 'everybody knows' facts."

I immediately filed this along with other well known facts about reloading:

You cannot push plain base cast bullets faster than 1000 fps without massive leading.
All .357 Magnums lead badly.
You can't get any accuracy with cast bullets in Marlin rifles.
You cannot use cast bullets in autoloading pistols.
You cannot use cast bullets in autoloading rifles.
Handguns are useless beyond 25 yards.

I know the only way to defeat these claims is to prove them wrong with actual data so I immediately set up an experiment.

Experiment setup:

I want to measure length as well as diameter. Previous tests on measuring cast bullets have demonstrated that measuring length is a real problem due to the mold seam at the tip of the bullet and the sprue cut at the bottom. It is difficult bordering on impossible to measure the length of a cast bullet with a flat point and get any type of consistent reading.  For this experiment, I wiped the tip and the base of each bullet on a piece of used 220 grit emery paper placed on a flat surface until I could detect no bumps or ridges.

It is critical that each measurement be of the same bullet as the last measurement so each bullet was identified as to which mold filling it came from and whether it was cavity 1,2,3, or 4.

Diameter measurements are taken perpendicular to the seam. Each bullet is marked on the base with a fine cut by an exacto knife showing the diameter to measure and each measurement is taken across that marked diameter.

The above photo illustrates how I kept up with the individual bullets so a separate record could be maintained of the measurements of each individual bullet.

On the right side of the block, you will notice one bullet with the nose colored red. This is my control bullet. It is the  same bullet, cast from the same mold with the same alloy but it was cast about three months before the experiment began.

The rows of four bullets are cavity 1,2,3, and 4 from a four cavity mold. Each row is a separate pouring.

You will also notice a screw driver bit. This is another control. I find it very difficult to measure the diameter of these bullets accurately, especially the as-cast bullets because they are not round. I draw a line on the base of each bullet to give me the location of the measurement. The sized bullets are significantly easier to measure because they are considerably more round than the as-cast.

The Screw driver bit was chosen for two reasons: It is not an antimonial lead alloy and should not be subject to any growth or contraction effects of the test bullets. It is hexagonal in shape and has flat sides making consistent readings much easier than a round test object.

Summary of results:

 

Summary:

Diameter

Length

Bullet 1:

Weight

D0-D

D1-D

D2-D

D3-D

D8-D

D0-L

D1-L

D2-L

D3-L

D8-L

Maximum

Minimum

Variation

Maximum

Minimum

Variation

Ballisti-Cast #651

158 gr SWC

161.0

0.36075

0.36075

0.36075

0.36075

0.36075

0.69960

0.69980

0.69980

0.69980

0.69980

0.36075

0.36075

0.00000

0.69980

0.69960

0.00020

161.6

0.36085

0.36085

0.36085

0.36085

0.36085

0.69995

0.70030

0.70030

0.70030

0.69980

0.36085

0.36085

0.00000

0.70030

0.69980

0.00050

161.5

0.36045

0.36045

0.36045

0.36045

0.36045

0.70014

0.70085

0.70085

0.70085

0.69980

0.36045

0.36045

0.00000

0.70085

0.69980

0.00105

161.6

0.36085

0.36085

0.36085

0.36085

0.36085

0.70075

0.70075

0.70075

0.70075

0.69980

0.36085

0.36085

0.00000

0.70075

0.69980

0.00095

0.00000

Bullet 2:

D0-D

D1-D

D2-D

D3-D

D8-D

D0-L

D1-L

D2-L

D3-L

D8-L

0.00000

Lee 379-250-RF

255.1

0.38120

0.38120

0.38120

0.38120

0.38120

0.92815

0.92815

0.92815

0.92815

0.92815

0.38120

0.38120

0.00000

0.92815

0.92815

0.00000

All 4 from cavity 2

256.7

0.38120

0.38120

0.38120

0.38120

0.38120

0.94430

0.94430

0.94430

0.94430

0.94430

0.38120

0.38120

0.00000

0.94430

0.94430

0.00000

255.6

0.38110

0.38110

0.38110

0.38110

0.38110

0.92610

0.92605

0.92605

0.92605

0.92605

0.38110

0.38110

0.00000

0.92610

0.92605

0.00005

256.6

0.38130

0.38130

0.38130

0.38130

0.38130

0.92725

0.92745

0.92745

0.92745

0.92745

0.38130

0.38130

0.00000

0.92745

0.92725

0.00020

 

 

 

 

   
 

 
 

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