My ancestor's cavalry regiment received its arms from the St. Louis Arsenal and had at least 70 .58 M.1841's in the later half of 1862. Through a combination of Moller's detailed chapter on M. 1841's, and McAulay's several pages in Rifles of the U.S. Army, I was able to determine that the bulk of the M.1841's receiving Colt long-range conversions (reamed out to .58, re-rifled, rear sight of the Colt M. 1855 carbine pattern, and a ring lug for a Collins & Co. sword bayonet) were Whitneys, and that 8400 of the 11,368 altered were shipped to the St. Louis Arsenal between May 4 and June 4, 1862. Through Moller's detailed description I was able to confirm that a seven-groove, .58 Whitney at a Missouri gun dealer was one of the Colt conversions shipped to the St. Louis Arsenal, right down to the #5240 reinspection serial and the "200" re-proof stamp on the left breech flat.