
The 3-inch ordinance rifle is easily identified by its sleek, tapered barrel and clean lines. At Gettysburg, it was the second most common piece on the field after the 12-pounder Napoleon; and it was the Federal's most common field piece. The 3-inch rifle normally fired Hotchkiss or Schenkel shells that weighed between 8 and 9 pounds (3.6-4.1 kg). In an emergency it could use 10-pounder Parrot ammunition. It could also be used to fire cannister but, as a rifle, was not as effective with this as howitzers or Napoleons.
Bore Diameter 3.0 in (7.62 cm) Tube Material Wrought Iron Tube Length 73 in (185 cm) Tube Weight 816 lb (370 kg) Powder Charge 1 lb (0.45 kg) Range (5° Elevation) 1,835 yd (1,678 m) At Gettysburg 146 (USA); 73(CSA)
http://einstein.human.cornell.edu/ACW/arty/3inrif.html