Here is the graphic of the Imperial Russian Zaibailkal Cossak, 1st Verkhneudinskii Regiment. Again, my best guess. Your tunic has had the "garde' bars removed from the collar and cuffs. Hope this helps.
Michael, I did not look closely at the buttons the first time. You're correct that they are field artillery.
Most of the artillery tunics I have seen have red piping. If I can find better reference I will post for you.