David Peppiatt, 59, of The Hydneye, Eastbourne, threatened to kill his son, Nathan, after seeing a photograph depicting him as an "urban terrorist" on the pub wall.
Julian Dale, for the defence, said the confrontation marked the climax of a feud over Nathan's dream of joining the National Front and his father's belief that he was neglecting his family by drinking away his wages. He said: "In short the way in which Nathan was living his life was abhorrent to Mr Peppiatt, and he very much wanted to shock him, and that, stupidly, on 13 February was what he set out to do."
Peppiatt pleaded guilty to possessing 50 rounds of ammunition and possessing a firearm with intent.
Sentencing him to 12 months in prison, Judge Richard Brown said: "Your behaviour in that public house was totally unacceptable. Fortunately your son, about whom I've heard many bad things, had the sense to try to cool things down."
Christine Lang, for the prosecution, said: "In an interview ... he said he didn't like the way Nathan dressed, his hair or the fact that he had an earring."