John,
Two 2.9" English rifles guns were turned in to the Ordnance Department back in December 1863, or early January 1864 when the militia battery was dissolved. The two remaining 2.9" English rifles were used in arming Company L, 2nd Missouri Light Artillery. (I am not sure what happended to the two guns turned over to the Ordnance Department.)
Beginning with its initial organization in January 1864, Company L, 2nd Missouri Light Artillery was equipped with four 3" Ordnance rifles and two 2.9" English rifles which were holdovers from the militia battery. (You can find numerous accounts in the Offical Records any many other sources confirming the Company L's gun composition.) After Thurber turned in Company L's two English rifles in March 1865, the battery was reduced to four guns and was equipped only with the four Ordnance rifles.
Please note, this will will be my last posting. I feel I have contributed enough information and have compromised my project enough.
Thank you for your interest in the batteries. Good luck on your research!
Gil