OK, Let's fix it.
Some language first.
The wedge;
Key
The holes in the stock the Key fit's through;
Key slots
Part of the barrel the Key fit's through;
Underlug
Part of the barrel that fit's in the stock at the back;
Breech Hook
Part of the stock the Breech Hook fit's in;
Tang
Remove the barrel. Observe the Key slots and how light looks when you look through them as they're lined up. Make sure the Key fit's freely through the slots without the barrel.
Replace the barrel, assuring proper fit of the Hook to the Tang. The barrel should drop down in to the barrel channel without (or very little) resistance. If you have to press the barrel down with anymore than light pressure we have a fitting issue at the Tang.
Now with the barrel in place look through the Key Slots again. Can you see the Underlug blocking any light as opposed to haveing the barrel out?
The typical answer is Yes. The underlug is blocking part of the Key Slots on the bottom.
Now that Underlug is actually kinda soft. The gun owner can adjust it too his likeing. If it is indeed blocking the slot, you can put your blade tip screw driver in the Under lug and twist. The twist will open the gap in the underlug so the Key fit's though, if you go too far you can tap it with a hammer to close it.
You can use the screw driver like a punch too and tap the end so it opens the Underlug.
If you have a Hook/Tang fitting issue come`on back and we'll work on that too.