A 56-year-old American man from Georgia pleaded guilty in Winnipeg court Wednesday to lying about having a gun in his luggage.
The Canada Border Services Agency said officers found an undeclared revolver when Curtis Carneal Roberson crossed the border on May 6.
The CBSA said it had been disassembled, but the cylinder was loaded.
Roberson has been sentenced to 45 days in jail.
People crossing the border must declare goods, including firearms, or face possible charges under the Customs Act.
CBSA said last year, southern Manitoba officers seized 21 prohibited firearms, 18 restricted firearms and 141 prohibited devices, most of them at Emerson