Cant speak for an m16, but I have absolutely carried an AR with collapable stock under my hunting jacket during inclement deer season weather. And that also includes a full size 1911 under said jacket as well.

Some say you can't hunt deer with 5.56, but the hydrostatic shock from a neck shot with 70gr soft point, shatters every vertebrae in the neck. Instantly drops dead on the spot, never have to track deer through the woods.