Thanks everyone for all the information! Yes, I found the obscure 9/64" allen wrench at the local hardware store. I torqued it down but loctite would be the 'semi - permanent' answer. No wonder I couldn't sight the d__m thing in! The rear sight is now at the top of its travel and all the way to the left.
Blue loctite... That still allows me to break the bond and get the screw out, right? Some loctite products are all but permanent.
I love the gun. I've put 500 of the cheapest rounds through it and it spit them all out (all, as in no faults); Remington bulk pack, Walmart bulk pack. Well, you get the idea; cheap ammo. Easy to field strip. Easy to clean. Fun to shoot