I replaced mine recently and I found the instructions by Zach S (post #6) in this thread to be invaluable:
http://www.thehighroad.org/sh...ossberg+safety
About 10 minutes ago, I just completed this job. Zach's post was invaluable. It's the only writeup of the Vang Comp oversized Mossberg safety replacement procedure that mentions tying down the trigger.
Here's how my install went:
1. Got a very thin-tipped tungsten edged screwdriver and really bore down on that security screw. It started to back out, no trouble. Closed action, set safety, zip-tied trigger back tight.
2. I put a large plastic bag over the back end of the gun, covering the safety mechanism for the final few turns of the screw, just in case anything was spring loaded.
3. I kept the gun in a vertical position. Important, as when you lift the OEM stock safety off, the ball bearing is seated by gravity only. In this case, the bearing stayed seated and no spring emerged.
4. Fitted the new detent plate. The hole at the far end second from the stock covers the ball bearing about 75 percent, so this is where your spring pressure is coming from. Unidirectional and no up-down issues. Only one way it can fit.
5. Wasn't sure about which way to seat the Vang Comp, but it made sense to put the fatter, wider end toward the stock, for your thumb.
6. Set the supplied screw with lock-washer in place and finger tightened.
7. Used the supplied Allen wrench to torque the Vang Comp down firmly, but not too tightly. The lock washer should obviate the need for Loctite, but if I'd had Loctite blue I would have used a bit.
Done. The new safety switch is much easier to operate and will be a blessing if needed in the dark under stress. This upgrade removes the principle weakness of the 500-series Mossberg and improves function. There's no reason not to do this.