Sadler has not previously appeared before courts.
Lawyer Lisa Thorsen told Judge Thomas Ingram her client had no memory of the incident and what occurred was out of character. It had shocked his employer and family when they learned about it.
Ms Thorsen said Sadler was remorseful, and had attended Alcoholics Anonymous and had alcohol counselling. The air rifle, she said, was unloaded.
She urged the judge to grant a discharge without conviction on the basis that Sadler, who had aspirations to travel overseas to advance his career, would be restricted in doing so if he had a criminal conviction.
Judge Ingram said he accepted Sadler was remorseful, the crime was out of character and he was doing something about his alcohol problems.
"The combination of an extremely drunk man in possession of a firearm and samurai sword and the potential for serious harm make this a pretty serious offence," he said.
Judge Ingram said he was not satisfied that the direct and indirect consequences of conviction were out of proportion to the gravity of the offence, and was therefore not prepared to grant a discharge without conviction.
Sadler was convicted and fined $1500 and $265.78.