Winchester trapper screw help identifying the threads.

[Alpha1]

Woe is me I have been having a devil of a job with my trapper getting consistent groupings I thought I had cracked it then to night the targets were a mess. I checked everything and the bad news is the williams rear sight if you get hold of it you can rock it side to side. I fear the worst I think the threads in the receiver may be duff. I would like to run a tap down them and fit some new screws. Does anyone know what the thread is of the drilled and tapped holes in the receiver the ones that normally have grub screws in that you can remove to fit a scope rail.
hmm

[Mattnall]

Possibly/most likely a unified thread, 8-36 or similar at a guess. Do you have thread or hole diameter and even better threads per inch?

[Alpha1]

Loctite is wonderful stuff.