The crown, or very end, of the barrel is very important and greatly affects accuracy of a firearm. The crown is the very last portion of the barrel that has contact with a bullet. A damaged crown may impart an unwanted spin or wobble to a bullet as it leaves the barrel. A barrel can be recrowned and smoothed with hand tools, with the barrel installed or removed from the stock. An 11-degree cut is a popular industry standard for most rifle and handgun barrel crowns.
Unload the magazine and retract the bolt. Insure there are no live rounds in the chamber.
Secure the barrel in a vice by using plastic or leather vice jaw inserts to avoid crushing or marring the barrel.
Attach a dovetail cutting fixture and secure it to the barrel, as close as possible to the crown. This fixture will be used as a straight edge guide, not for cutting a dovetail.
Place a few drops of cutting oil on the file and use the file to true up (square) the muzzle.
Install the recrowning reamer in the tap handle. Add a few drops of oil to the muzzle and insert the pilot bushing of the reamer into the bore. Turn the tap slowly (clockwise) to cut the crown. Re-oil as necessary and cut until the muzzle face is crowned.
Use the sandpaper to smooth the face of the crown and remove tool marks. This is best done by hand with sandpaper over your thumb.
Install the brass crowning tool in an electric drill and dip the rounded tip in lapping compound. Insert the rounded tip into the crown face and operate the drill at slow speed. This process removes fine burrs the crown cutter leaves behind on the edges of the rifling where it meets the crown.
Clean the barrel to remove oil and metal shavings. Insert a cotton swab into the muzzle and slowly retract it. Look inside the muzzle where it meets the crown. If small cotton fibres are left behind, it means there are still burrs and the crown needs more polishing with the lapping compound.
A crowning tool and crown reamer (cutter) are different tools. The reamer has blades that cut the angle into the muzzle. The crowning tool is a cylindrical brass tool with a rounded head for polishing.
Always clean and oil the barrel before firing ammunition through it.