Mossberg bolt action firing pin nut adjustment

[jdereede]

I am resurrecting a Mossberg 185 K-A 20 gauge bolt action shotgun. It is in very good working order, except that the firing pin nut has unscrewed from the nose of the firing pin.

I need to establish the correct depth to thread the nut on the nose of the firing pin and the proper means (the threads look mildly scored) of retaining it.

Anyone's help or guidance towards success will be appreciated. Thanks!

 

[Chawbaccer]

I don't have anything except a wooden ruller handy to measure with but I have a gun like yours in 20 guage ant the pin is a bit over 7/8 past the nut which is showing two threads on the stem and protudes about an eighth past the bolt face. The nut just appeats to be tensioning the spring so I don't know if it is critical. Educate me if I am wrong as I am not a student of this gun. If you need more accurat measurements let me know in a couple days.
By the way, releasing the striker with the bolt out of the gun hurts.