Just doing some inspection on a lot of Daudetaeu N12 (6.5x53.5 SR). As it is well known, this cartridge has a design and/or manufacturing defect that causes longitudinal cracks on the case neck. Then the oxygen and humidity trigger the corrosion mechanisms to end up in this disaster:
After doing more inspection on the units (more than 40 units) I have come up with:
* The head stamped units DAUDETAUE N12 (Keller & Co. 1893 - Austria) have a circular shaped powder:
- Then the SFM units have a rectangular shaped powder. SFM stamped and G de U units:
Some comments and questions:
- From 10 “G de U” units, 9 had the rectangular powder but just one bears the circular style powder as the Australian unit. These units was dated 1896 and does not look to be re-loaded units.
- All the SFM (about 10) have the rectangular powder
- The manufacturing defect that could generate the neck cracks is the annealed. It is a thermal process to relieve stress or tension on the metal after stamping. A bad annealing or not performing this process can be the root cause of this well known defect. However, the annealing is a thermal process that combines temperature and time, something that is set for each lot and each manufacturer can have different settings. In any case we can see the same defect on the cases form Keller and SFM, also the same defect for cases made in different years. My suspicion is that the root cause is multi-cause and not only linked to the annealing. Thoughts?
- it looks like two stamping die of the headstamp G de U 1896 were used, there are small differences. This was new for me.