RE: 410 Slugs And Full Choke
I shot quite a few rifled slugs through a full choked H&R 16 Ga. They shot just fine. I heard or read somewhere that Remington Sluggers were made undersized because they knew folks would shoot them from full choked guns.
If you have other chokes for the gun try them. If you don't, just shoot the rifled slugs through what you have. I don't believe you will damage the gun.