Within Canada, rifle magazines for semi-automatics are limited to 5 rounds. 5 rounds of whatever they’re designed for. So what happens when you design a STANAG-compliant magazine for the enormous 50 Beowulf? You get a magazine that can legally hold 14-15 rounds of 223.
***Update Nov 18, 2015: The RCMP considers these “dual use” magazines and considers them prohibited. Read more here.***
According to RCMP bulletin 72, magazines are limited to the capacity of the round they were designed for. Here’s the exact wording: “The capacity is measured by the kind of cartridge the magazine was designed to contain. In some cases the magazine will be capable of containing more than 10 rounds of a different caliber; however that is not relevant in the determination of the maximum permitted capacity.”
A Quick Video on 50 Beowulf Magazines
Where to Buy 50 Beowulf Magazines in Canada
Armtac sells Alexander Arms 50 Beowulf magazines.
Northern Republic Magazines carry the Alexander Arms Mags as well. They’re about $100.
Your other option for 5+ round capacity AR mags are the LAR-15 style pistol magazines.