makinbacon

As the Title states I have an M1014, and this is what i've found. I acquired and shot my M1014 for the first time this weekend using RIO low recoil rifled slugs. I was absolutely thrilled by the function at the range and had a great time as I got though my merger 25 shells in short order with some really great groupings at 25 feet. Once I returned home and started the cleaning process, I ran my bore cleaner and got it back to beautiful no time; until I ran a bore light though and noticed some fairly substantial grooves towards the front 3-5' of the bore. It appears the slugs gouged out the bore to a point when I ran my finger over it's noticeable and not just residue. Is this normal or did I just screw up a $2k shotgun my first trip? I've been told by multiple people, that should have been no problem running these slugs, attempted to locate any section in the manual too but couldn't find anything.