u/HenriqueNikasso

Does anyone know where these primer designations come from?

In ballistics, many designations have a clear origin (dimensions, manufacturer, or historical — like Boxer/Berdan). But in these cases (1½, 2 ½, 5 ½, 7 ½, 9 ½, 209…), it looks like just a numerical sequence.

Are these related to physical dimensions, standardization (SAAMI/CIP), a specific manufacturer, or some historical origin?

If anyone has technical or historical references, I’d appreciate it!