A South Australian farmer says he was lucky to avoid a more serious penalty after importing materials into Australia to make firearm silencers.

In Mount Gambier Magistrates Court on Friday, Naracoorte farmer Stephen Zilm was sentenced on charges of importing and possessing prohibited goods.

Zilm had ordered three solvent traps on a US online site in June last year, with the intention of making silencers for firearms used for pest control on his farm.

The solvent traps, designed to attach to a gun's muzzle to catch cleaning solvents, are readily available via online auction sites, and can be adapted to make silencers or sound suppressors.

In South Australia, it is illegal to possess or manufacture a silencer or device used to muzzle noise from a firearm.

The farmer told ABC South East he knew firearm silencers were illegal when he imported the traps, but said he did not understand importing material to make them was also illegal.

Zilm said he and his pregnant wife had been shocked when their property was raided by Australian Border Force officers in September.

"I had this knock on the door in the morning and there were 15 guys standing there, all armed," Zilm said.

"I had no idea until they said they were looking for silencers."

Officers seized Zilm's computer, mobile phone, and six additional solvent traps from his gun safe.

Gun safety taken seriously

Zilm, a Country Fire Service volunteer and member of the Naracoorte Pistol Club, said he took gun safety seriously and had genuine reasons for wanting to minimise gun noise, including protecting his own hearing and looking out for the wellbeing of his flock.

"If you're just blasting away, the sheep run away scared and leave their lambs," he said.

"I had them [solvent traps] all locked away in my gun cabinet and didn't think there was a risk to anyone else. I didn't realise there was such a big penalty."

In her judgement, magistrate Theresa Anderson accepted the farmer's reasons and described Zilm as an "intelligent man".

Zilm, who pled guilty to both charges, received a three-month suspended sentence for the importation charge and a four-month suspended sentence for the possession charge, to be served concurrently.

He was also placed on a 12-month good behaviour bond.

The maximum penalty for importation of prohibited or restricted goods is 10 years imprisonment or a $275,000 fine.

Cautionary tale for other farmers

Thankful to avoid a more serious penalty, Zilm said his story was a cautionary tale to other farmers who may be looking to purchase such items online.

"The internet is free-range. Being out in the country, it's a lot easier to buy things online," he said.

A brief search revealed overseas sites selling solvent traps openly advertised the fact they were happy to ship to many countries, including Australia.

Zilm said using the word "silencer" leant the items a more ominous air — farmers commonly called them suppressors or sound moderators.

"Calling them silencers makes them sound like the movies," he said.

"You can buy them over the counter in other countries. I really didn't understand the seriousness of it."