Simple possession of a restricted firearm can carry a maximum of a 1 year jail term or a $5,000 fine. If there is reason to believe that you had dangerous intentions, or if children or drugs are found nearby, the charges can be much worse.
Trafficking offences carry a minimum of 3 years in jail for a first-offence, to a maximum of 10 years.
Likewise, other offences become significantly more serious if committed with a weapon.