thats what i was thinking. its a 5/8 dia hole too. theres a bolt hole going through the mag case directly over the center of it when its assembled.
Exactly what I was going to say. They have similar spots on my 394, i couldn't figure out why the tank wouldn't come out even when I had all the anti-vibe mounts unbolted... Then I found those stop screws. If your hard on the saw put a decent amount of hard silicone in those holes, otherwise they rub through and create a leak. I had to epoxy 2 holes closed because of them (previous owner must have dropped it a few times). I epoxied them closed and put a nice thick coat of silicone in there, now the bolts act just like anti-vibe mounts themselves.
Like McCall said, if you want to be really safe about that exposed bolt, you can do some fancy stuff with that hole. You can take a 5/8" hole saw, saw out a "plug" from a hockey puck, and slice a piece it to fit the depth of the hole. The inner drill bit "hole" will fit right over the end of that bolt that protrudes into the hole on the tank. That will be more durable than the silicone idea. This method is going above and beyond, but if you are anal like some of us, you will find creative ways to make things. Not necessary, I believe, but what can it hurt?
I have made quite a few annular buffers for Stihl saws out of hockey pucks and hole saws.
99 cent hockey pucks can make 3 annular buffers... A lot stiffer than the real deal, but a lot cheaper when scrounging for parts.