There's an interesting & entertaining small book titled "The Colt Whitneyville-Walker Pistol" by Robert Whittington. The narrative is about the production of the Walker & it's use in the Mexican War. He also cited several reports from the field, including from Capt Williamson, " They have been more or less damaged by firing, and the wear & tear of some eight months use in the field. In some cases the cylinders are entirely destroyed-in others the barrels are irreparabley injured where they join the cylinders-and again, having bursted at the muzzle, the barrels have been cut off to one half their original length."
I sorta conjectured that the cut-off barrels was a field expedient to make this handsome but unwieldy revolver easier to use.
PS: I also doubt many, if any, were used in the Civil War, & if so, probably some Texians who "liberated" them when their service was up in Mexico.