They'd want nothing to do with it but not because of any safety concerns. These feckers want to arm teachers and children in schools so safety is far from the top of their priority tree.
3D printing will continue to improve with regards quality and spec. Their issue is more with the idea that people buying their own materials and printing their own products removes them and their members as the middle men along with the premiums they currently charge on their products.
It won't only be the gun crowd, this is going to be widespread as this tech develops further and Johnny Public starts printing his own products at home. Expect way more government regulation, investigation and scaremongering (actual scaremongering, not the Brexit red herring) about things like food, tech equipment and clothing as lobbyists start to see their profits drop and start bullying their pet politicians to remember where their bread is buttered.