10" groups at 100 yards is unimaginable... I can't even begin to think that a bad barrel would be that bad. You say you had the barrel re-crowned, so I'm assuming you already disassembled and rebuilt the upper to check for issues? Perhaps you are shooting too heavy a bullet with too open of a twist. Are you slinging 180gr out of a 1:12 barrel? If I had a 10" group with a supposed "target" barrel, I'd be out to beat someone! I believe MADUCE owns one of these, but I'm not sure he's shot his yet. Perhaps he'll chime in here for some better answers.