The rearsight is dovetailed on but it's tight for a reason you adjust the windage by bashing the foresight, IIRC if the rifle is shooting to the left of aim whack the foresight over to the right a little bit, shooting to the right of aim,whack to the left.
Ben
PS I did say If I Remember Correctly, and it was 30 years ago when I last adjusted one , so some brain fade is to be expected