.50 with a laser assisted round. (Assisted = you have to fire within 10 MOA vs. Guided = fire in the direction and forget) The technology is there. A previous employer didn't want to go there so we canned the effort..... However
, there is technically an obscure public domain 'how to' on this in the key technology areas (putting it in the obscure public domain was to impede others patent efforts in the relm). Is a virtually guaranteed hit for that big buck @ 2 miles in light winds worth $100/round?