I agree with Longknife about the Corps of Discovery using specifically “short rifles”. The military part of the Corps also had muskets as documented in the journals.
It is true that the fully developed Harpers Ferry 1803 rifle was not developed until December, 1803 at the earliest, well documented in the correspondence of the day. Lewis had his rifles shipped west in the summer of 1803, so they weren’t fully developed HF 1803’s. However the govt ordered 4000 of that first 33” barrel rendition, and ultimately paid for 4015. The rifle that Ernie Cowan dissected (found in a Saint Louis antique shop many years ago in percussion with patch box inlet covered with a scab of wood and serial number 15 on the barrel) has all the earmarks of a prototype HF 1803 rifle with distinct differences from the post-December, 1803 production.
The argument that Lewis took 15 gun slings from Harpers Ferry for his supposed “full stocked contract rifles” ignores the fact that he would have wanted replacement slings for the muskets that also accompanied the expedition.
I believe the 15 short rifles prominently mentioned in the L and C journals were the 15 prototypes made by HF as they were developing the “Model 1803 Rifle”, were the extra 15 paid for above and beyond the 4000 fully developed 1803’s, and that one has been found and well documented by Ernie Cowan.
The Lewis air rifle has also been located and well documented and identified. Fun history!
Bill Paton