Forget what you have seen on UTube, and elsewhere, about the Lewis & Clark air rifle; it is based on misinformation; here are the facts, supported by documented research: Prior to the Expedition, Meriwether Lewis bought, borrowed, or rented rifle taken on the Expedition, from a Pennsylvania watch and clock maker, Isaiah Lukins, who, as a watch/clock maker, also made air rifles and air canes, as part of his business, located at Horsham, Penn. until 1791, when he moved to Philadelphia. He died in 1847. After his death, an auction was held, selling off his personal effects, which included "turning lathes, nautical/chemical/other instruments, gold chronometers, gold clocks, steam, cutting, & dividing engines, tools, etc., etc. (105 items on original auction list, DATED MONDAY, JANUARY 4TH, 1847), including 12 Air Cane Guns, one small air gun, and two large air guns, one of which was #95 on auction list, described: " 1 large air gun, made for, and used by Messrs. Lewis & Clark in their exploring expedition. A great curiosity."
This Lukens air rifle is located at the Virginia Military Institue Museum, in Jackson Memorial Hall on the Campus. Part of the significant contributions to this museum was the collection of one Henry Stewart,VMI 1935 graduate, which included the Lukens, Lewis & Clark air rifle. It is of .31 caliber, butt reservoir. Lewis mentions it 21 times in the journals, and not once was it ever mentioned that it was used for hunting anything (numerous modern day reports indicate that it was used for deer hunting, which is false). After the Expedition, in the fall of 1806, Lewis had the rifle returned to its maker, Lukens.

References: Too numerous to mention them all, but three of the more important ones will suffice: Proceeding on to the Lewis and Clark Airgun. Airgun Revue, Volume 6, April 2000; Pp 13-33.

The Air Gun of Lewis and Clark, American Rifleman, August 1984 Pp 36-37, 80-81.

The Lewis & Clark Expedition Air Rile "A Great Curiosity," Ray Nelson