Re: Replacing Safety
Put the shotgun in a padded vise, with the bolt locked to the rear.
You have two options. I've done both, and actually was able to get through a large number of departmental guns with the second method which is quicker and safer obviously. Sometimes you have to destroy the screw though.
1. Dremel method-Mask off the receiver around the safety with heavy tape. Use a cut-off wheel and cut a cross slot in the screw head, being careful not to cut all the way through. Once you have a slot big enough for a small driver just back the screw out. Replace safety and use a new screw.
2. Driver method-You may want to mask the receiver just to keep from scratching it since some force may be needed. The best tool is a gunsmith's driver, sized wide enough to fit the screw head. Gunsmith drivers are squared on the tool edge, and not beveled. That's why you frequently see scratched/worn screw heads on guns: people don't have or use gunsmith drivers and the beveled tool edge slops in the squared slot, allowing the driver to fit loosely and mar the screw head. Press down on the screw head with the driver and back it out. You may want to tap the handle of the driver with a nylon mallet to seat the driver bit and help it bite into the screw head. Back the screw out while pressing down.
Tips for both-
Make sure the bolt is locked to the rear. That way the mechanism doesn't drop into the receiver.
You can use a small dab of grease to keep the ball bearing from falling/rolling out of the recess in the receiver.
If your safety comes with a backing plate (the metal piece with 5 holes in it) USE IT. It helps to prevent wear on the underside of the safety, which can result in the safety flipping on after each firing. Be advised that some safeties don't come with them, but still need them. These usually don't include ANY other parts like the screw, detent, and spring and you basically just get the safety button. Brownell's sells the safeties as a kit, and also just the button itself in some cases, so be aware of what you will need.
It may be a good idea to make sure that your safety comes with a new screw. Not all suppliers include the screw, and if you ever need to replace the safety it is a lot easier with a conventional screw or a hex version. I've had to help several people that cut through their safety screw only to find out when they open the safety packaging that they don't have a screw to secure it with now.