On interlibrary loan I received the 'Post Returns' for Pine Bluff, Arkansas, from November, 1863 to early 1869 (roll #928, N.A.R.S. microcopy No. 617). There are no returns from December 1863 through December 1864, perhaps the most interesting year of Pine Bluff's Federal occupation. However, on that November, 1863, return (actually a tri-monthly return rather than a 'Post Return' proper), the First Indiana Cavalry is listed as possessing 3 pieces of artillery of 2.9-inch caliber. Since this is the second contemporary document I've seen which reports the caliber as 2.9-inch, perhaps that question is settled? By January, 1865, the First Indiana Cavalry is no longer at Pine Bluff and the 2.9-inch guns are gone, and never return to that post.