"Hart's Battery, armed with four mounted guns, and commanded by Capt. William Hart was re-designated as the 2nd Arkansas Field Battery and assigned to the Reserve Battalion.[39] [40] "

I am wondering if the "Four Mounted Guns" is not supposed to be read as "Four Mountain Guns". (I.E. model 1841 12 pd. Mountain Howitzers). These guns were quite common in Trans Mississippi service and would explain why Harts Battery was assigened to the reserve corp being armed with those weapons.