Reitz (1975:103) observed “matchable striations on unfired primers of [exhibits from particular lots of] Winchester, .38 special cartridges.” These marks were attributed to a particular punch used during the primer seating process, which had not been produced to the same smoothness as is typically the norm. “These markings remained prevalent even after firing, which could be perilous to comparison examinations by unwary examiners.” Similarly, Robinson (1996:164) observed Russian-made ammunition with primers that, before firing, “had parallel marks like one might find as a result of breechface impressions.” Finding that “the marks continue around the curve of the primer into the sides which were not visible,” he concluded that “the only way that marks could have gotten there was by the rollers in the brass mill where the sheets of brass were made.”
The third class of marks, those that are problematic for comparison, include ammunition types with existing distinct parallel and cross marks on the primer surface, making it difficult to discern which textural features were created by firing. Murray (2004:314) reports on toolmarks on the primer surface of Fiocchi .25 Auto ammunition whose cause is unknown; the manufacturer suggested that they might be attributed to a rare, imperfect configuration of the feeder during the process in which the primer is seated in the empty shell. The marks were problematic because they were not consistently prominent across the whole primer surface. When, as in the Wolf ammunition toolmarks, the markings span the whole primer, an examiner can compensate for them because they can be traced from the face of the primer into the pit of the firing pin impression. Maruoka (1994a; see also Maruoka and Ball, 1995) had previously noted parallel marks on the primer surface of some Fiocchi ammunition, but those marks did span the entire surface. But these inconsistent marks offer no such traceability, so that “differentiating these marks from breech face marks would be very difficult, if not impossible” (Murray, 2004:314). Some ammunition may also bear random marks on the rim of the cartridge that could be mistaken for ejector marks.