Just before Mary Ellen pops a paper bag behind John Boy's head, he loads a spent shell into the shotgun. He subsequently "fires" this spent round.
The shotgun that John-boy is using in the beginning of the episode is a 10 or 12 gauge and yet the first time he fires it there is no kick. A gun of that bore would at least have jumped enough to have required John-boy to take a firmer stance.
When Elizabeth is in bed in John-Boy's room, she tells him to carry on writing. The actress playing Elizabeth starts to say: 'Richard' and corrects herself to say: 'John-Boy'. Richard Thomas is the real name of the actor who plays John-Boy.
As a country boy who probably knows basic gun safety, John-Boy would know better than to rest a 12 gauge shotgun, which has a significant recoil, on his forearm while firing it.