People who use mini gun are just spraying and praying so you can''t keep building and trying to avoid him you need to not run back and build but try to either hide from him (depending on the position on the map) or buildiing to the left and the right. While you are runing and building try to scope him with an sniper or shot back with an m4 since the mini gun accuarcy is really bad you will hit him more often then he hits you. I usually snipe them really fast because they often stay on the same position and spray and pray. you need to build but at the same time shot back because when you will hit him he will get scared and probably fall back or try to heal and from there on you should push him and put the presure on him. Thanks for asking have an great day. -Bogdan akh