It doesn't matter how modified the gun, the ammunition, and how great the sights and the assassin is. A Mauser C-96 is incapable of the level of accuracy required to make the shot. Even when this show was filmed, this 19th century firearm would have been considered an antique.
At the airport tarmac, Chin Ho is shown painting a white line around the shot person lying on the ground. In a few seconds he is seen holding the paint brush, but there is no white paint on the brush.
In one scene, Steve McGarrett's car is shown driving on the left side of the road.