In my opinion, any ruling that affects gun sales for anyone that is in the business will be frowned upon by the NRA. Gun sales are big business. Limiting assault rifle sales in the way you suggest means fewer people own them, hence less gun sales. Not an option.

It's a fact that gun sales go up after mass shooting. This simple fact means any sort of regulation will always be fought by the NRA. Again, it's about money. The organization is facing banruptcy due to cases in NYC. Money talks.