Go to forge or custom game mode and press X to go to settings.

Make it to where you have unlimited ammo and that your two weapons are sniper rifle and the second is your choice.

Next go back to the menu where you can choose your map. Choose the map called "the pit" and start your game.

Once the game starts, go to one of the buildings (easier on forge to do this) where on the floor above you is the little target guy in the windows moving.

Go to the floor below that or in an open spot where you can see the cieling. If you look up, you should see what looks to be a yellow dot(s). Follow it and zoom in.

It should be this small little yellow bird (there are a lot of them). What makes it more challenging than shooting the birds in the Guardian map is that the birds are unpredictable(they move randomly) and they are alot smaller too.

So if you can get used to this, and get good at this, you will be able to snipe anyone.