870 Wingmaster 20 gauge with magnum cartridge steel pellets

[Synchronizor]

The 3.5-inch or 89mm super magnum 20ga does exist, but it's very uncommon. It's pretty much a dedicated slug shell used in special single-shot shotguns with rifled barrels. There is no 89mm super magnum version of the 20ga 870 (though there is a 12ga super magnum 870). A current-production 20ga 870 Wingmaster should have a 3" or 76mm chamber, which will also handle 2.75"/70mm or shorter shells. Again, double check the markings on the gun's barrel to be sure. It's an American gun, so it'll be marked in inches.

[Fabien]

Ok, thanks Synchronizor,

I understand better now ! .