I'm really surprised there is no one offering a 4.6mm AR upper.
The AR-57 5.7mm upper is really cool, and works great full auto with the slide fire stock. You can shoot dime to quarter sized groups at 7yds full auto with one of those with ease.
If stuck with a semi that cannot have an affixed stock anyway, as a US civvie legal MP7 pistol would be if ever imported, you might as well just go with a much more light and compact Five SeveN. It'd probably be 1/3 the price, and perform just as well to boot. An Mp7 carbine would look retarded with a 16" barrel, so it'd have to obviously be SBR'd. I'll bet it would cost at least triple the price of a slide fire equipped SBR'd AR-57 too.
Neat gun, but even if they ever were imported, i couldn't see dropping $3-5000 on one. I guess if i was a rich man though, sure, why not.
