What is the parent case used to make the Jamison line of cases? I have seen reference to .257,.264,.284,
.300,.338,.350,.375,.416 and .458 bores. What kind of performance are they capable of?

the 404 jeffery... they are essentially the WSM line, although not direct copies

jeffe

404 Jeffery is correct. I have 338 Jamisons and 338WSM's. The water capacity of the cases is virtually identical except for the fact that the RWS cases used for the Jamison are more substantial and a bit heavier. Fired cases hold exactly 1.2g less water. 83g for the WSM using WW brass and 81.8g for the Jamison using RWS brass.

404 is correct. Originally he used a Westly Richards case with severely rebated rim, but then he discovered that the 404's did what he wanted and were much easier to find to boot. - Dan