Hi Holly,
I have a green laser of the type on the bay (around £25)...it is ok/good fun for plinking, in fact a .22 pellet will shine out and act like a tracer for part of its trajectory if the laser is mounted above the barrel. The dot is clearly visible to the naked eye out a 50 yards but it it probably wouldn't be fine enough for what you want...also it may be a bit glary depending on the mag/scope your using.