Questions about repairing the safety on the Mossberg 500 series come up every so often. Since I had to take a buddy’s 500A apart to fix the safety, I figured I’d take some pictures and write down what I’ve learned about this particular job.
The location of the safety button on the 500 is ideal, but the design leaves a lot to be desired. Fixing the safety is probably the most common repair on the 500 series. There are two reasons why you might have to fix the safety on a 500:
1. The safety button, which is plastic on some 500 models, broke.
2. The shotgun performed the Mossberg “disappearing safety button” trick. The safety button is held in place by a single short screw that goes through the safety button and threads into the top of the safety block inside the receiver. If this screw works loose, the safety button and some of its ancillary parts will go flying.
The one piece of good news is that repairing the safety is fairly simple, although thanks to some silliness on Mossberg’s part it takes a fair amount of time and labor to really do it right. But if you can detail-strip and reassemble the gun, and if you’ve got a Dremel or other rotary tool handy, you should be able to make the repair no problem.
These are the parts that make up the safety mechanism. From left to right, they are:
Safety button screw
Safety detent plate
Safety detent spring and safety detent ball
Note that the screw shown here is not a factory part. More on that later.
If the gun performs the “disappearing safety button” trick, it’s often possible to recover the screw, the button and sometimes even the detent plate. Most of the time, the spring remains in its hole (check the detent spring hole in the top of the receiver before you order one). The detent ball is pretty hard to find, because it’s so small and it goes flying under spring pressure. The safety block will stay inside the receiver.
A look at the top of the 500’s receiver gives you an idea of how they all fit together. The top of the safety block fits up through the slot in the top of the receiver. Note that the safety block is shaped kind of like a hook. During reassembly, the opening of the hook needs to face forward.
The detent spring goes into the hole in the receiver, just forward of the red dot. The detent ball will sit on top of it. The detent plate and then the safety button need to be laid gingerly on top of the safety block and detent ball so that the hole in the button is aligned with the screw hole in the safety block. The screw then goes down through the safety button and detent plate and threads into the safety block.
Because the safety button can go flying off the gun if the screw works loose, you’ll want to use some blue Loctite on the threads. Reassemble the gun right away and make sure the safety works properly before the Loctite sets.
Two words about the parts to use. First, Brownell’s lists two safety buttons. Except for the part number and the price, you won’t see any difference listed. In fact, if you were to order both you’d see that they look almost identical from the top. But the $6 button is plastic, and the $16 button is aluminum. The plastic buttons have a reputation for breakage, so $16 for the aluminum button is money well spent.
Second, I recommend that you DON’T ORDER A FACTORY SAFETY BUTTON SCREW FROM BROWNELL’S OR MOSSBERG. The screw that Mossberg currently sells is a one-way screw—half of each side of the slot is rounded in such a way that you can tighten it just fine but you can’t loosen it--the screwdriver will just skip out of the slot. This means that if you ever did have to take the screw out—to replace the safety button, for example, or to replace the safety block—you’d have a problem on your hands.
Instead, order a packet of #6-32 “Fillister Head” screws from Brownells. They sell a whole kit made up of these screws, but you’ll really just want to order one of the refill packs of #6-32s. These are 1” blued-steel screws, and they’re $5-$6 a pack. If you want to cut corners, you can pick up a #6-32 x ½" hex-head screw from a hardware store, but be warned that the head of the screw will stick up above the safety button a little bit.
The correct length for the screw’s shaft is roughly 5/16”, so whether you buy a 1” screw from Brownell’s or a ½” screw from the hardware store you’ll need to shorten it. This is where the Dremel tool comes in. With a 1” screw you’ll want to cut it off close to the final length and then grind it down the rest of the way; with a ½” hardware-store screw, you’ll probably just want to grind it. The screws from Brownell's are nice and hard, so be patient when cutting and grinding.
Once you’ve got it down to the correct length—in other words, when it’s just short enough to screw all the way down into the safety block—you’ll want to use some cold bluing on the tip where you’ve exposed bare metal. If you don’t already have some, be sure to order it when you’re ordering the parts. The screw shown above is a #6-32x1" fillister-head screw from Brownell's that's been shortened and had its tip re-blued.