Do a Google search for "Lewis and Clark air rifle" and you will get a bunch. I've been following this story for some time now, and it's interesting to read the forensic evidence that leads to the conclusion that THIS one gun is the one that made the famous trip.
It has to do with the fact that Lewis documented the number of shots fired with one magazine loading. It provides support that this is the one gun that was modified to shoot smaller balls, allowing for 22 shots, where the unmodified guns only hold 21 because of their larger size.
Another bit of evidence is that the gun was repaired at one point along the journey, documented in the journals, and this gun shows that repair.
A fascinating bit for me was that the gasket that contains that 800 psi in the tank from leaking when the attachment is made to the gun is made from HORN.
Also interesting to read about the adoption of airguns by the Austrian military, and how the tanks were recharged in the field. Each man carried two extra charged tanks. The unit given these incredible repeaters were the ones considered the most loyal and trustworthy. After all, a mutiny by conscripts armed with this firepower was unthinkable to the monarchy.
It's a fascinating story. If you like history AT ALL, this story is worthy of your time. Google it.