removing breech knob

[angelinga]

I was trying to take out the back plate so I could remove the hammer. It said to unscrew the lock on the breech opening knob so I could remove it. The manual said to turn it out until it stops then take out the set screw. However it would not unscrew enough for me to take off. I don't know why that is and answers would help!

Pic:
http://i27.photobucket.com/albums/c165/kitbh/rasta.jpg