there is no magazine capacity limit for manually operated action shotguns, and rifles.
all shotguns come with a hunting plug to limit magazine capacity to 2 rounds, which is the legal limit for hunting game birds. Because its not a semi-auto you can load it up with 10 rounds so long as you're not hunting game birds with it, in Alberta anyways, not sure about other provinces. You'll have to check your local reg's. I've also seen longer hunting plugs to limit to 2 rounds with the mag tube extension installed. I believe tacstar says minumum barrel length for the 10 rounder was 26" so I'm geussing you'll have 2" of barrel past the mag tube. Still cool looking though, the squirrels arent going to like this!
