three general types of ball valves according to bore

A full port ball valve has an over sized ball so that the hole in the [ucl=from-www.valve-ball-manufacturer.com]steel ball[/ucl] is the same size as the pipeline resulting in lower friction loss. Flow is unrestricted, but the valve is larger. This is not required for general industrial applications as all types of Valves used in industry like Gate Valves, Plug Valves, Butterfly valves etc have restrictions across the flow and does not permit full flow. This leads to excessive costs for full bore ball valves and is genearlly a unneccessary spending for customers.
In reduced port ball valves, flow through the valve is one pipe size smaller than the valve's pipe size resulting in flow area becoming lesser than pipe. But the flow discharge remains constant as it is a Multipler factor of Flow discharge(Q) is equal to Area of Flow (A) into Velocity (V). A1V1=A2V2 i.e the Velocity increase with reduced Area of flow and Velocity decreases with increased area of flow.
A V port ball valve has either a 'v' shaped ball or a 'v' shaped seat. This allows the orifice to be opened and closed in a more controlled manner with a closer to linear flow characteristic. When the valve is in the closed position and opening is commenced the small end of the 'v' is opened first allowing stable flow control during this stage. This type of design requires a generally more robust construction due to higher velocities of the fluids, which would quickly damage a standard valve.
A trunnion ball valve has a mechanical means of anchoring the ball at the top and the bottom, this design is usually applied on larger and higher pressure valves (say, 4" and above 600 psi and above).