Anyone familiar with these shotguns? They are the old mossberg 16 ga. bolt actions. I am trying to take down the bolt. I need to remove the firing pin nut to remove the pin and spring. The problem is the nut is round with two small slots on the top of it. Looks like a special wrench is needed, like the type for the mauser stock through bolts. Can this be removed with conventional tools, or is a special tool needed? And any suggestions where could I get one if it's needed? Thanks in advance for any help.