You do realize you should still pattern a gun anyway. You'll find you can adjust patterns from the same choke using different shot types.
Anything hard, for instance steel typically brings chokes up to the next constriction, magnum shot, not magnum loads but the shot is harder. If a load was put together w that you'd prob get a decent pattern. Cheap loads may be loaded w cheap shot that's softer. More flattened shot, more fliers, more holes, small birds.
I'd say instead of or besides asking a forum find out what your gun/load can do on a patterning board.
