If the spring goes solid the slide stops on the bushing and not on the guide rod head. This is no bueno.
Assemble the gun with the guide rod but no recoil spring, run the slide to the rear until it stops, mark the slide/frame with something. Put your recoil spring in and do it again. The marks should match up. If not trim a coil and try again.
I've had to cut a coil or two from every ISMI recoil spring I've replaced.