John,
I have not looked at my research involving the history of the batteries for quite some time due to my involvement with several other projects. I went home and reviewed my notes and wish to correct some of the information previously provided to you.
Wachsman's Independent Battery, Missouri State Militia Light Artillery was originally organized in May 1862 with four 2.9" English rifles, one 12-pdr. mountain howitzer and one 6-pdr. field gun. (The English rifle lost in the late summer of 1862 was replaced by a 6-pdr. field gun. In September 1863, Thurber's Battery, Missouri State Militia Light Artillery was comprised of three 2.9" English rifles, one 12-pd. mountain howitzer and two 6-pdr. field guns. (Please note, the battery was never equipped with a James rifle - my error!)
I came across in my notes that in February 1865 Major General Grenville Dodge ordered Co. L, 2nd Missouri Light Artillery to forward its two 2.9" English rifles to the Benton Barracks Arsenal. (I've got a copy of the request somewhere - could not locate it!) I have no idea what happended to the two guns after that.
Hopefully this may assist you in your research.
Gil