I have never heard of a rifled choke. If there really is one, it would have little effect on a slug with the short amount of time it would go through it. Rifled slugs through a smooth barrel should work fine for you. You should have a way to mount an optic on that model shotgun to make it even more precise.
Do you have interchangeable choke tubes for your 935? I looked and Mossberg says the waterfowl model includes them. I don't know what choke you have, but you should carefully check the point of impact before shooting. At a defensive shotgun class I took one guy had an adjustable choke that made the gun shoot more than a foot left of point of aim at 40 yards.
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