I have an old Stevens. Recoil operated. So if I rack the slide and have the pump forward I can not pull the trigger. I thought It was broken. After some great gn research I learned about the recoil operation. If you tap the gun on solid ground barrel up. It trips the recoil operation. I believe mine is 520b. Also says something about browning patent. It’s able to slam fire.
So in closing if you put your pump forward and can’t pull the trigger. Gun is broken. I will buy for parts. Lol