Excuse me,
but what pressures are encountered with the 375 H&H rimless in a Double? 62,000 psi? What are the max velocities attained by ?270 gr bullets with proper regulation?

Side note re: dust and rifles. Sounds weird but In very dusty environments I actually tape saran wrap over the crown end of the barrel. Sounds comical but it doesn't affect the bullet trajectory and this keeps foreign debris out of the barrel.