John, Larry -
The two-pounders likely were Woodruffs, or something very similar. Woodruffs, however, were not of cast iron, but rather wrought iron, as Woodruff described : "They are manufactured from the best charcoal scrap iron, faggotted, brought to a welding heat, and forged, and thoroughly compacted under a heavy trip hammer, then turned, bored, and polished."
I looked up the "Record of Events" of Co. L of the 1st Missouri Cavalry, MSM, in the "Supplement to the O.R" (pt.2,vol.34, or serial no. 46, pp.536-537). Brief notice there was taken of both August, 1862, actions (Lt. McLaren's with "first section" of 2-pounders, and Lt. Caldwell's "third section" of 6-pounders). In Nov.-Dec. 1862 it was noted that one 2-pounder was left at St. Joseph, and one 2-pounder and one 6-pounder was "in possession of" Col. McFerran at Lexington.
Lastly, an entry for March 22, 1863, lists the killed (from Co. L) at Blue Springs: John Donnelly, George Garner and Jesse H. Wollery; these names can be added to the Nebraska boys killed that day.