Having long wanted a precision .223 bolt gun that uses AR mags, and finally done a lot of research on it lately, turns out the problem is that the geometry of the AR 15 magazine itself does not lend itself very well to the vast majority of bolt designs.
The Mossberg and the Rugers which use AR Mags both have unconventional features built into them to facilitate use of these magazines.
The issue with the stock options isn't that they can't use the mag, but that the action can't.
It would almost make more sense to build an AR with a match grade barrel and then block off the gas so that you have to #### it after each shot. The UK AR market actually has some special goofy looking BCG designs that include cocking handles for this purpose. Unfortunately they would still be restricted in Canada.