>>584944
The following is a general procedure for getting rusted parts un-stuck.
Grab your choice of penetrating oil. Kroil, B'Laster, whatever. WD-40 is weaksauce. Soak it down, let it sit for a couple hours.
Get a brass rod, wooden dowel, or otherwise non-marring drift, and a tiny little tappet hammer. Put the drift on the part, and hit the other end with the hammer. Give it a couple of taps and see if you can get it to move. Never hit it harder, get a bigger hammer.
Did it budge? Apply more penetrating oil, and tap it back to where it was. Work it back and forth with the drift. If you try to force it one way you'll just wedge it in place and then you'll be really fucked. The idea is to work the rust loose and flush it out with periodic applications of penetrating oil.
>>584929
That looks remarkably similar to my Remington Model 151. Is it a case of convergent evolution, or did somebody go full Chinese Knockoff on someone else?