Picked up a rough romy  build with a romy barrel. From the muzzle to about 1/4" back is gouged and scraped and looks like someone tried to smooth it out. It shoots ok but getting about 6"-8" groups at 50 yds. What about counter boring back past the "bad" part ? What kind of bit is needed to cut the hard chrome , carbide,or colbat? Bit size ? Could it make things worse ?  Any advice or opinions ? -Thanks

You should drill out the damaged area '' with a new bit ''so it is at least 1/16 larger than the bores deepest point using a bit with an 11* head if possible. Once the damaged area is drilled run the bit backward very lightly to get a more even depth. You then need to use an augger bit or a sanding type bit to get the new crown even. After you have the new crown even and with no drill lines you should use a series of wire brush bits to get the entire area you worked on polished smooth.