From "Unit Organizations and Orders of Battle of the Great Armies of Europe, 1853- 1870" by J.W. Brown:
"… A battery contained eight pieces of ordnance. Two of the ordnance in each field battery were 6" howitzers, the remaining six guns were either 6 pounder smoothbores or rifled 6 pounders. There were a few batteries equipped with French LaHitte system rifled 4 pounders. The heavy batteries contained six 12 pounder smoothbores and two 5.6" long barreled howitzers…"
"… The Guard artillery had one battery of Horse Artillery. This battery had eight guns…"
His orders of battle show the following:
At Calatifimi: 1/2 foot battery with 6# smoothbores
At Milazzo: 1 foot battery with 6# smoothbores
At Volturno: 1/2 foot battery with 6# (not otherwise identified) and 1 heavy foot battery with 12# in the Royal Guard Division; 1 foot battery with 6# rifles, 1/2 heavy foot battery with 12#, 1/2 LaHitte battery with 4# rifles (may be horse artillery), 1 1/2 foot batteries with 6# rifles in the 2nd Cacciatori Division; 1 LaHitte battery with 4# rifles (may be horse artillery) and 1/2 foot battery with 6# smoothbores in the Reserve Cavalry Division.
Hope this helps a little.