I would not shoot any slug through a full choke barrel, especally the foster type slugs. Shooting slugs through a barrel that is choked to tight will tear up the thin lining on the inside of the barrel.
I would let her shoot the 20 gauge with the most open choke tube you have for the gun. Typically this will be Improved Cylinder. Shoot a rifled slug through an unrifled barrel.
Andy
I would let her shoot the 20 gauge with the most open choke tube you have for the gun. Typically this will be Improved Cylinder. Shoot a rifled slug through an unrifled barrel.
Andy