My last zabala unmentionable sxs had screw in chokes and that had swollen exteriors at the muzzles.Can you feel a bulge on the inside?
I think Britsmoothy is kinda right and it left the factory that way.
Would suggest it was destined to be screw in chokes but didn't.
It was rated for 3" high pressure steel too.
Of course we don't know what other contract barrels Pedersoli make. Maybe the wrong two got mixed up in the wrong bin!