This paper investigates the error incurred by predicting the wave-induced heave forces on a submerged body using a mathematically simple flat face bow and stern rather than the typical curved ones. We examine both theoretically and experimentally how the heave force changes when flat end faces replace hemispheric end caps. We consider bodies with various length-to-diameter ratios to identify the influence that the ratio of the end cap length to the total body length plays on the heave forces. We also consider bodies with forward speed to identify if heave forces are affected by leading edge separation around the blunt front face which is not present for the hemispheric end cap. The theoretical predictions are from an existing potential flow analytical solution while the experimental results were collected in a towing tank with wavemaking capability. The theoretically predicted percent increase in the heave forces caused by the flat end face was confirmed by the experimental results. Finally, the theoretical predictions also showed that the percent increase in the heave force is independent of the forward speed of the body. This was also confirmed with the experimental results.