Colt AR15 9mm Carbine.

[Sentryduty]

Jim, Not even the 10 Round Mags ? What's going on up there ?

Well, the magazine body size isn't regulated, the capacity is, in a semi-auto centerfire rifle/shotgun we are capped at 5, a pistol magazine may hold 10. (The are other nuances to this but are not directly related to the discussion)

The real issue is the song and dance required to get the magazines pinned/blocked prior to, and then properly imported etc. It's not impossible, but it's not as smooth it could be.

Basically, if you decide you really want/need something like this from the US you are generally limited to dealing with a import broker, which can make a bargain into a cost prohibitive venture once those fees are paid.

Just the nature of things is all.