| OBERMEYER RIFLED BARRELS Quality Rifle Barrels Since 1962 23122 - 60th Street Bristol, Wisconsin 53104 |
| Exterior Finishes and Installation Guidelines |
 |  |  |  |  |
Finishes
Barrel blanks are finish turned. Standard round sporter and target barrels are polished. Service rifle
barrels are turned to a basic shape; since they still require finish machining, they are not polished.
Bead blasting is a good method for finishing the exterior. It gives stainless steel barrels a dull gray
finish, and it is potentially beneficial for chrome-moly barrels (even if they have not been blued)
by holding oil, which may help inhibit rust.
Fluting
When a barrel is ordered with flutes, the outside diameter will be filed and polished prior to
milling. The flutes will normally be cut after the blanks have been drilled and finish turned, prior to
reaming and rifling. The installer is responsible for polishing the flutes and for any additional
polishing of the OD. Target barrels may be machined to include optional skips, or non-fluted
spots, to allow for the positioning of barrel-mounted scope bases, such as those used to mount
Unertl, Lyman, and Mitchell target scopes.
Installation Guidelines
Barrels are finished at least 1 inch longer than the finish length. This allows the muzzle end to be
cut off, resulting in the removal of any tool run-out. The reaming and rifling procedures leave the
least run-out at the muzzle end. Chambering removes run-out on the breech end.
Muzzle crowns are extremely important with regard to accuracy. In a fair number of cases, barrels
which performed poorly have been fixed by re-crowning. Small differences at the point of exit can
allow gas to blow by the projectile in an irregular pattern, causing the bullet to tip. Many people
believe a crown angle of approximately 11 degrees is ideal, although I have found no basis for this.
I suspect they are mistaking the care taken in the machining for the actual merit of the particular
angle. The problem with such sharp-corner crowns is that they wear unevenly, either from gas as
the bullet exits or from cleaning. I finish crowns by using a 60-degree piloted center reamer. First,
I place the barrel in a lathe and face the barrel with a recess to protect the crown. Second, I
insert the piloted reamer in the tailstock chuck. Chucking the reamer is better than attempting to
do this by hand, because the rigidity of the machine reduces any tendency to chatter. Third, I
put the lathe in neutral and turn the barrel by hand, slowly making a light cut with the reamer to
break the edge of the crown. I do this manually, not under power, in order to further avoid the
possibility of chatter resulting from the increases and decreases in cutting loads that occur when
the tool alternately contacts land and groove areas as the barrel spins.
The extra muzzle-end length also provides a place to center or chuck the blank during installation
machining of the breech end. The best procedure is to rough ream the chamber in a lathe, using a
steady-rest for support. (This type of proper set-up should provide good alignment, which an
improper set-up will not. Do not, for example, attempt to thread and chamber while supporting
the work near the breech end in a 3-jaw chuck, with the remaining length hanging unsupported
through the spindle hole.) Use the rough chamber resulting from a proper set-up to locate the
center for finish turning the shank and cutting the thread. See the FAQ page for additional
information on bore diameters and reamer pilot recommendations.
These tips are offered for the information of individuals having the necessary education and
background to assess their value with regard to specific projects. They are not intended to form
a complete training and instructional program in themselves. All other persons are advised to
seek the services of a professional gunsmith for barrel installation and installation-related
machining work.
Barrel blanks are finish turned. Standard round sporter and target barrels are polished. Service rifle
barrels are turned to a basic shape; since they still require finish machining, they are not polished.
Bead blasting is a good method for finishing the exterior. It gives stainless steel barrels a dull gray
finish, and it is potentially beneficial for chrome-moly barrels (even if they have not been blued)
by holding oil, which may help inhibit rust.
Fluting
When a barrel is ordered with flutes, the outside diameter will be filed and polished prior to
milling. The flutes will normally be cut after the blanks have been drilled and finish turned, prior to
reaming and rifling. The installer is responsible for polishing the flutes and for any additional
polishing of the OD. Target barrels may be machined to include optional skips, or non-fluted
spots, to allow for the positioning of barrel-mounted scope bases, such as those used to mount
Unertl, Lyman, and Mitchell target scopes.
Installation Guidelines
Barrels are finished at least 1 inch longer than the finish length. This allows the muzzle end to be
cut off, resulting in the removal of any tool run-out. The reaming and rifling procedures leave the
least run-out at the muzzle end. Chambering removes run-out on the breech end.
Muzzle crowns are extremely important with regard to accuracy. In a fair number of cases, barrels
which performed poorly have been fixed by re-crowning. Small differences at the point of exit can
allow gas to blow by the projectile in an irregular pattern, causing the bullet to tip. Many people
believe a crown angle of approximately 11 degrees is ideal, although I have found no basis for this.
I suspect they are mistaking the care taken in the machining for the actual merit of the particular
angle. The problem with such sharp-corner crowns is that they wear unevenly, either from gas as
the bullet exits or from cleaning. I finish crowns by using a 60-degree piloted center reamer. First,
I place the barrel in a lathe and face the barrel with a recess to protect the crown. Second, I
insert the piloted reamer in the tailstock chuck. Chucking the reamer is better than attempting to
do this by hand, because the rigidity of the machine reduces any tendency to chatter. Third, I
put the lathe in neutral and turn the barrel by hand, slowly making a light cut with the reamer to
break the edge of the crown. I do this manually, not under power, in order to further avoid the
possibility of chatter resulting from the increases and decreases in cutting loads that occur when
the tool alternately contacts land and groove areas as the barrel spins.
The extra muzzle-end length also provides a place to center or chuck the blank during installation
machining of the breech end. The best procedure is to rough ream the chamber in a lathe, using a
steady-rest for support. (This type of proper set-up should provide good alignment, which an
improper set-up will not. Do not, for example, attempt to thread and chamber while supporting
the work near the breech end in a 3-jaw chuck, with the remaining length hanging unsupported
through the spindle hole.) Use the rough chamber resulting from a proper set-up to locate the
center for finish turning the shank and cutting the thread. See the FAQ page for additional
information on bore diameters and reamer pilot recommendations.
These tips are offered for the information of individuals having the necessary education and
background to assess their value with regard to specific projects. They are not intended to form
a complete training and instructional program in themselves. All other persons are advised to
seek the services of a professional gunsmith for barrel installation and installation-related
machining work.