I have seen a pellet migrate to the right heart. More often, I have seen the pellet or BB traverse the myocardium or the right atrium and 'seed' into the trabecula of the right ventricle. If the pellet passed thru the wall of the right heart, the stakes are antied up. Now one has to worry about pericardial effusions and tamponade. It is not likely, and in a normal healthy young boy would probably heal uneventfully. With an older person, the recuperative abilities are diminished, as well as the ability to stave off infection and other physiological insults. The man needs to be in a tertiary care medical center. Move him to the Houston Medical Center now.
I'm quite worried to ask what tamponade is.