a wall that is a gun turret,but with limited ammo .(maybe a electrical turret that dont gain energy from grid,instead,it only fill energy when place,and when mined,it drop a out-of-ammo gun wall so you can refill it)

keep doing this,we might just got a walls modpack XD

Yeah, the point is, I don't really see the benefits of ammo walls. They need to be refurbished individually (-> lots of inserters) or have a recipe that does that, so you'd deconstruct and reconstruct over and over again. It is not a mechanic you'd want in early game and late game you just could use electric weapons to do the same... They don't use resources and have better damage against biters

you are probably right,I just think of early game gun turret nest clearing,