screw question

[LookMomNoSights]

Does anyone know the screw or should I say threading specs of the 70's Kmag stabilizer insert?  I want to find a screw or hex bolt or whatever looks decent for my Kmag just to plug the hole and keep junk out of there.  I held a flashlight to the hole and can see bare riser wood at the end of the tunnel.  Dont want anything getting in there,  especially water!  

[lpcjon2]

I would use 2 part epoxy and sawdust to make a filler that you can stain the same color as the riser.

i think its 5/16 s

[LookMomNoSights]

The insert is in the bow,  its not a bare hole.  I just wanted to screw the right size and thread pitch screw into the insert to plug it.  Dont really want to have to take it into the hardware store and test a million screws or hex bolts if I can help it!