The chamber cast shows 6 lands and groves and the twist is 1-29". The rifle barrels appear to be chambered for the 10.5X47r.
Remaining Questions
Do you think that the #380 is the serial number?
Do you think that the crown over V above the 16 inside the circle is the "in stock" mark of 1891 ?
Is the stylized SS above the proof marks the barrel makers/fitters mark?
Anyone familiar with Witten ER steel?
Otto