Once again 343 ruins a supposed to be good playlist. Railguns spawn like crazy and youre dead if you are caught without one. I just had like a triple railgun kill happen in a game where me and my mate and an enemy had a railgun. Its like whats the point when you can just crouch in the hallway with a railgun and wait.
It takes time for the Rail Gun to charge, you can hear the enemy charging it and finally it's easy to dodge if you know how to time it.
Since you are unable to listen for someone charging a weapon you know they are using, I guess it would be safe to assume the dodging part might be a little advanced for you.
If I know I can kill someone over and over again with a weapon/strategy, I will continue to do so until you find a strategy that can out do my current one.
If you learn the maps, keep your distance, use your angles and shoot at the same guy your teammate is shooting at then you will have no problem. The further away the rail gun pointed at you is, the easier it is to dodge same with rockets.
OR you can just keep complaining about losing to a forum that doesn't care. Or you can learn the game and work on your weaknesses. Or ask for help.