Yeah, I understand the crusher pressure measuring system, and CUP vs PSI etc.
The Poms also used a copper crusher system, but they located it at the breech instead of through the chamber wall.

The main reason for my question about the 30" test barrel is really related to whether the velocity for Winchester factory .458 ammo was quoted as from a 30" barrel, or was it recalculated down to the 25" length of their Model 70 rifle barrel?