Not carried this out on a Rifle Mod situation but in the workshop many times including Red
Use Aerosol brake cleaner but not all brake cleaners work! look for a chlorinated high strength formula, that will soften it to a workable state, the solvent is thin enough to work between locker and thread, once you’ve loosened it up, then apply more solvent, you may need to work back and forth depending on how much thread locker has been applied.
Other solvents that can be used, trichloroethylene, toluene, and ethylene dichloride also MEK if you have any military mates?
Oh and make sure you are in the fresh air
Not sure what it will do to the finish on the items mentioned
Good luck