Replacements - S1-E4
Other mistake: When Heffron is taking his throw at darts, he states that he needs a "double seven". When he takes the throw, the dart goes into the treble eight (an earlier close-up confirms that the board has the standard Gamlin configuration), yet, from the reaction he gets, he's made the throw he was going for. (00:04:40)
Answer: That actually is the clip. It is loaded into the top of the rifle, and is ejected with the last round. See http://www.wwiitech.net/main/usa/weapons/m1/.
J I Cohen