Patent ID: 8684083

Claim:
An apparatus for use in perforating a wellbore casing, comprising: a charge holding structure including a first end, a second end, and an internal cavity between the first and second ends, wherein the internal cavity is adapted to contain at least one perforating charge; a first end cap that is positionable generally adjacent the first end of the charge holding structure; a second end cap that is positionable generally adjacent the second end of the charge holding structure, wherein the first and second end caps are respectively interconnectable to the first and second ends of the charge holding structure such that the charge holding structure is rotatable relative to the first and second end caps about an axis of rotation, and wherein a central axis of each of the first and second end caps is spaced from and substantially parallel to the axis of rotation; a first substantially straight reference line defined along an outer surface of the charge holding structure and extending between the first and second end caps; a second substantially straight reference line defined along the outer surface of the charge holding structure and extending between the first and second end caps; and a reference plane defined through the first and second reference lines, wherein the first and second end caps are respectively interconnectable to the first and second ends of the charge holding structure such that the reference plane remains in a particular orientation regardless of an orientation of either of the first and second end caps when the apparatus is disposed in a wellbore.