Dave,

For starters, the 1st and 2nd U.S. Sharpshooters (Berdan's) were initially issued Colt revolving rifles. They were rearmed with Sharps rifles in the spring/summer of 1862.

Your source for the rifles being issued in general is likely Coates' and Thomas' book, which pertains mainly to the 1863-1864 time period.

It is going to be somewhat difficult for you to determine what Union regiments received Colt revolving rifles in 1861 and 1862, as most of the quarterly Federal regimental ordnance reports that I've seen from the NA do not begin being made until mid to late 1862.

Mike