Since the speed of the bullet coming out of the barrel was about identical to our present day 30-30, that was about the same performance that could be expected out of the 30/40 rifle.

The 30-06 - being roughly 1000 or more fps faster - was a big improvement over the 30/40.

One reason for not upgrading the Krag was due to the fact that it only had one locking lug on the bolt. It could not handle the chamber pressure of the 30-06 round.