My SMLE

[Richard Hare]

Ovidio,

If you have reloaded the Hornady brass a few times, it is very likely fatigue causing your cases to fail. The .303 is rather hard on cases, and we sometimes only get a few reloads before case separation.
There are ways to extend case life, such as only neck sizing or minimal case sizing, but these rifles will stretch the cases more than some other types. Maybe do a search on case separation.

To remove a stuck case, run another round into it, and then extract. It will usually pull out the remains. Or, a good screwdriver with a blade wide enough to grip the walls of the failed case;
Push it into the case, twist, and the case usually comes out. For this it makes sense to sharpen the sides of the blade very squarely, so they bight into the case walls.
I have had a good few cases fail over the years, and the screwdriver or another round have always extracted the bad case.
I do not think it is a headspace problem, it is just what these rifles tend to do with reloads at a certain point.
If a case has been reloaded a few times, and a wire it inserted into the case mouth, sometimes a groove can be felt a few mm in front of the rim, where the case is about to separate. Another warning sign, is a ligther coloured line around the case, and this is where the brass is stretched thin and will fail .

Hope this helps!
Richard.