If you live in Ontario, you must plug your shotgun so ONLY 2 rounds fit within the magazine well. This is the LAW! and you will have every MNR officer you come across check your gun. It is how they get payed... so you bet they will check you. The reason for the 3 shot maximum as *taken directly from NMR officer*
"After 3 shots, your risk of wounding or maiming the animal raises beyond acceptable limits. If you can not hit it or kill it in 3 shots, you better god dam find it or you need to spend your time learning to shoot and not hunting."
And a tip about hunting, It may be called buckshot but it is the WORST round you can use to hunt with. If you absolutely must use a shotgun to hunt deer or large game. ONLY USE SLUGS ****ONLY SLUGS****.
Now that you have a nice mossy you can buy an interchangeable slug barrel for it. They pop in and out really easy and real fast. So you can even put the barrel in your pack and change it out on the fly. Just remember it must match your magazine, or else the end locking nut will not line up with your magazine. So just make sure you order the right barrel for your magazine size.
hope this helps