The Britannia field pieces are not particularly crisp, judging by those photographs. I don't know what they are supposed to represent, the blue is a weird color (as carriages were painted a dark olive color), and I am not sure why the gunner/sergeant is holding a stick. Cavalry pieces would have been the M1841 mountain howitzer (short bronze muzzle-loading tube, with sub-caliber breech), on either a pack carriage or a prairie carriage. There would have been some 3-Inch Ordnance Rifles in wrought iron black tubes, but the muzzles did not flare out and there were no raised bits on the barrel around the trunnion; those were mostly held at forts and fortifications, as the weight and size made cross-country travel in the West very difficult. In the early 1860s, there were assorted scraps and unwanted pieces like 6-pound field guns rotting in the depots and in the hands of volunteer units. There were also Hotchkiss 1.65-Inch mountain rifles appearing in the late 1870s, but those also did not have a flared muzzle, and a very simple and straight barrel.