It's 3mm x .05mm
I would drill it out and tap it for 6-48. Take a #31 drill bit and drill out the hole and then get a 6-48 bottom tap and tap the hole. I will only take you about a minute to do and if you do this you will be able to find a bead to fit any where in the world.
Would a Remington thread fit this gun
No but if you tap it for 6-48 it will.