Originally Posted by

**mks**
Damon,

Oops, I have my numbers wrong. Olin cartridge brass alloy 260 yield stress varies from 10 ksi to 33 ksi annealed and from 21 ksi to 93 ksi roll tempered (work hardened). Tensile strength varies from 45 - 61 ksi annealed and 49 - 104 ksi rolled.

The same concept still applies, though. If you run the calculations, what you find is that the deformation becomes more elastic and less plastic with each sizing and firing. For BR spec chambers, strains are less than 1%, which even for the most work-hardened case means that the material never reaches the tensile stress at which failure occurs. For instance for a 30 BR with 0.002" clearance, the strain is 0.65%. Failure thus eventually occurs due to cyclic fatigue, which may take thousands of cycles. Or a defect in the material.

It takes at least about 0.004" clearance for the brass to reach tensile stress (split necks) for the most work-hardened state. But this large a clearance is, in general, not BR quality.

Cheers,

Keith