Dimensions

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Deformation and distortion make it difficult to measure the dimensions of pellets, limiting the number of pellets that can be used as a basis for determining shot size.

The steps for this procedure are as follows:

Perform preliminary procedures.
Determine the total number of pellets received.
Determine the composition of the pellets.
It may be useful in some cases to enlist the aid of an instrumental chemist in determining the composition of non-lead shot.
Determine which pellets are suitable for measuring. For example, determine which pellets roll freely; pellets that roll freely should be measured.
Measure and record the diameters of the pellets in hundredths or thousandths of an inch. For small pellets, it is generally appropriate to record three decimal places; for buckshot, two decimal places are appropriate.
Determine the shot size of the evidence shot by comparing to a standard table of shot sizes. Note that industry sources indicate shot designated as a certain size may vary up to plus or minus half a shot size.

Rule of 17

The theoretical diameter of shot is calculated as follows:

Diameter of shot = 17 – shot size
Where all measurements are expressed in hundredths of an inch
For example, for No. 6 shot:
- Diameter of shot = 17 – 6 = 11 (or 0.11 inches in diameter)
Note: This technique does not work for buckshot.

Click here to view a table on shot sizes weights.

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