1.Establish
a population of Sb in WCC/MC bullets (Guinn’s
14 test bullets).
2.Find
the distribution by plotting. Normal? No. Lognormal? Yes.
3.Choose
two fragments that might be accidental match (Q1 and Q9, with Q9 as reference).
4.Calculate
standard normal variates for these fragments.
5.Area
between them is probability of chance match. Double the area to allow second to be higher or
lower.
6.Result
= 2% probability of chance. (2%–3% for matches in other group)
7.Drops
by 10–100 X for random ammo (i.e., to 1/1000 to
1/10,000).
8.Drops to 0 for cores of pure lead or hardened lead.
9.Conclusion: Single chance matches ruled out.