The railgun is the newest addition to the backyard arsenal. Boasting the 2cd highest base damage per shot out of all the towers (400 damage at level 1!), (quake tower is highest) the railgun can make short work out of most lesser monsters. This is an extremely effective tower, just like the laser tower, so its best to put it beside your Storage Silos,Town Hall, Resource Harvesters, or anything lootable. The tower does however have a very slow fire rate and a very limited lock on range. This is made up for by it's infinite line of fire. This means what ever the tower locks onto (the first monster to come within range) it will fire at hitting that monster and every monster directly inline with the first. Like the Laser and Cannon towers, this tower is best used with the pathing of blocks, more specifically in a straight line (the Laser hall of death, two blocks in a straight line with the Railgun at the back, example below). It fires more damage than Laser Tower, and shoots an infinite line of fire, but has a longer delay before it can shoot again.
Effectively using the railgun
However powerful this gun is, it's very inconsistant. The railgun can preform outstandingly by hitting 20 monsters in 1 shot (8000 damage at level 10) or get stuck shooting at 1 dave while all the other monsters are mere inches off to either side of fire. The railgun does not attack flying monsters(Teratorn, Fomor and Zafreeti) except for Balthazar, so it would be wise to protect it with a Sniper Tower , Tesla tower , or Aerial Defense Tower .
You are going to want to place this gun at choke points where monsters funnel together because this gun rely heavily on pathing for effectiveness. Building a long hallway to the gun is a good method. Or simply place it around a corner to shoot monsters as they round. Also keep in mind the railgun can NOT target flying monsters(Teratorn, Fomor and Zafreeti). Make sure that it's guarded by other towers, as it can be easily destroyed when it's under attack because of it's slow fire rate.It is recommended to be guarded by high level blocks .