You have a couple choice, shorten the screw a little, run a ¼-20 nut on it, cut or file the screw down, then run the nut off to clean up the threads. The other choice, just use an O-ring or two to take up the slack, it will semi-float the forend in the process.
You may also be able to put a spacer on the screw before you install it, I don't have a survivor stock any more to look at it, seems it had a shoulder on it, but I don't remember now!!
Glad ya got a handle on the misfires.
Thanks,
Tim