The rifle supposedly used to shoot Harrow is explicitly stated in dialogue to be a .276 caliber and the rifle shown is a Garand, which was chambered in .276 Pedersen in its experimental phase, but, aside from the ..276 T3E2 Garand being incredibly rare and expensive (in the six figures), the rifle shown is an M1D model chambered in .30-06.
In addition to the comment about the bullet, it also shows a boat floating in a human heart and a car driving on a fingerprint. It is the opening credit art not reality.
The gall bladder is on the right side of the body, Harrow was shot on the left side.