The opening in the receiver of the pre-1899 musket is 3 5/8" compared to about 3 1/4" for one of my 1895's. This is about the difference in length between 30-40 Krag and 303 Savage loaded rounds. In other words the bolt would be about 3/8" longer and the receiver proportionally longer.
Maybe the cocking indicator bolt was a prototype for the 1899 bolt.
David
That's interesting. It shows you can lengthen the basic design for longer cartridges. I guess, conversely, you too could shorten the receiver for smaller cartridges. Thanks for taking the measurements.