The numbers on JSB produced pellets (also sold under Airarms, Cometa and other brands).
For example on the label on the bottom of the tin:
First number: 8006709
Second number: 6
Third number: 4.51
The first number:
– 8 = number of the pressing die
– 00 = personal number of responsible employee in production
– 67 =personal number of the employee in Quality Control
– 09 = year of production is 2009
Second number: 6 = manufacturing batch
Third number: 4.51 = head diameter in millimeters
The 2013 production year batches I have seen do not show the “personal employee” numbers anymore. They just show zeros at those positions. The number looks like 8000013 for a pellet from pressing die 8 from the year 2013.
Die numbers higher than Die 9 make a the total number an 8 digit number. Like 21 00 58 14 : Die 21, production employee 00, Quality control employee 58, Year 2014.
I for myself ignore the head diameter and just look at the die number when selecting batches for testing.
Pellet head size and weight distribution
I searched the internet for info on the weight and head sizes that are found in a tin of airgun pellets with the same head size and batch number.
The above table about H&N Field Target Trophy pellets were measured with a digital caliper. Not by clamping them between the jaws but by lying them on the jaws that were opened to a pre-set distance. No deforming of the pellets this way. Notice that the tin with the 4.52 label has an average measured head size of 4.55 and the tin labeled 4.53 has an average measured size of 4.47. (source: http://www.network54.com/Forum/184474/thread/1297810495/H%26amp%3BN+FTT+4.50+head+size)
The above picture shows JSB Exact pellets that were air gauged. See http://www.network54.com/Forum/451309/thread/1380753871/ for more info. The picture shows that the head size varies from 4.49mm to 4.52mm in one tin.
The picture above shows the weight distribution of a full tin (496 pellets) of Airarms Field Heavy. These pellets are produced by JSB. The pellets were sorted in 0.02 grain / 0.013 gram groups The lightest pellet is 10.16 grain or 0.658 gram. The heaviest is 10.52 grain or 0.682 gram. The label says the pellets are 10.3 grain / 0.67 gram.
This picture above shows a very good weight distribution of JSB Exact. A narrow and normal distribution with most of the pellets at the average weight.
The picture below shows a bad weight distribution: A wide distribution with many light and many heavy pellets.