If a law enforcement officer decides to seize your firearm and or parts the onus will be on you to fight the seizure and or charge and defend yourself......
There is often no penalty to the officer but of course much in the way of grief/hassle/expense and stigma for you to defend it.
This is the problem.
Most of them have no idea of the details of current firearms law....
Basically they can seize your firearm, charge you and when the charges don't stick ....oh well you get the gun back and cover your legal bills and time off.
Whether they seize it cuz they think it's too short/too scary/too powerful....
Carrying the condensed version of the Firearms regs makes squashing an unlawful seizure or charge a lot easier...when you can show the officer the info hard copy in real time and or quote and reference it...otherwise they have the power and you are powerless.
If a LEO is going to seize your short shotgun based on their perception that it is illegal yer prolly screwed anyway and will face the hassle of defending yourself to not only get your gun back but to stave off a criminal charge. Pretty much guilty till you prove yerself innocent with firearms law.
I know the 1st time a conservation officer saw my 14in 870 they were very freaked out and would likely have railroaded me had I not remained calm and quoted the actual law and fervently hammered them with the actual law and relevant information.
Pretty confident if you polled a random handful of cops they wouldn't have a clue how long a shotgun barrel is allowed to be by law and or whether it is relevant if it was cut down/mass produced/gunsmith repaired etc....you'd get a blank stare .....
Same goes for barrel length with rimfire/centrefire/shotgun/rifle...mag capacity/semi/pump/bolt/lever.....
At the end of the day there is no "field test" to confirm if your shotgun barrel is legal or not.....it would have to be determined forensically by the RCMP...... after it was seized, you're charged and it plays out in court. Having a receipt, stamping it or anything else wouldn't matter.
The LEO has the power....they can let you go on yer way or they can seize yer gun, charge you and let the chips fall where they may.
Your best bet is to be knowledgeable with the law, be able to articulate it, remain calm, assertive, respectful and be prepared to challenge unlawful actions.
Ask for a full name, badge number and their immediate superior's same info if/when they are going down the path of seizure and or challenging the veracity/lawfulness of your firearm and or your actions.