At about 12.30pm, police searched a property at Penola and located a homemade pen gun.
On closer examination police discovered the gun was loaded with a .22 calibre bullet.
The 46-year-old man from Penola was charged with numerous firearm offences including aggravated possession of a firearm, breach of bail and breach of an intervention order.
He has been refused bail and will appear in the Mount Gambier Magistrates Court later today.
Anyone who has any information about illegal firearms is urged to contact Crime Stoppers on 1800 333 000 or online at http://sa.crimestoppers.com.au
You can remain anonymous.