There are only four pistols recorded as being taken on the Lewis and Clark Expedition and all four were "owned" by Capt. Lewis. Two, were obtained from the Schuylkill Arsenal in Philadelphia and it is assumed that they were of the North and Cheney pattern, a copy of the common French military pistol. Lewis also purchased " 1 Pair Pocket Pistols, Secret Triggers $10" from a private merchant. These were probably a cased pair of those little screw barrel pocket pistols with folding triggers. Pistols are mentioned several times in the Journals and they are always in the hands of Capt. Lewis. With only four pistols recorded for a group of 33 (Actual number is not verified) men then in this case I would say that pistol's were uncommon on that journey.
On another note here is a interesting entry that Capt. Clark made in his Journals December 4. 1805.
"""" Soon after Several Canoes of Indians from the village above came down dressed for the purpose as I Supposed of Paying us a friendly visit, they had Scarlet & blue blankets Salors jackets, overalls, Shirts and Hats independant of their Usial dress; the most of them had either war axes Spears or Bows Sprung with quivers of arrows, Muskets or pistols, and tin flasks to hold their powder; Those fellows we found assumeing and disagreeable, however we Smoked with them and treated them with every attention & friendship"""""