Cut and Crown a Vent Rib Shotgun Barrel

Used shotguns with long barrels are readily available in most areas.  A 28″ vent rib shotgun is great for the duck blind or goose hunting, but too long for many other hunting and sporting applications.  In this post, we will look at how a vent rib shotgun barrel is cut and crowned (a screw in choke system will be installed as well).

The following items were ordered from Brownells:

All lathe work is conducted on a Grizzly gunsmith’s lathe.

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The barrel used in this post is a Remington Express 28″ vent rib barrel.

Cutting a vent rib barrel requires a little more planning than a plain barrel.  The new crown needs to land on one of the rib bases.  If not, the unsupported rib would bend and the finished product would look awful.  I'd like this barrel to be around 18" long.   I'll cut the barrel a little over 18.5" so I can have the muzzle aligned with a rib base.

Cutting a vent rib barrel requires a little more planning than a plain barrel. The new crown needs to land on one of the rib bases. If not, the unsupported rib will bend and the finished product would look awful. I’d like this barrel to be around 18″ long. I’ll cut the barrel a little over 18.5″ so I can have the muzzle aligned with a rib base.

A chop saw makes quick work of the cut.  I ran the rib against the fence which yielded a cut perpendicular to the axis of the bore.

A chop saw makes quick work of the cut. I ran the rib against the fence which yielded a cut perpendicular to the axis of the bore.

Note the difference in thickness between both side of the barrel.  In this case the bore wasn't centered in the barrel. The wall on the right side of the picture is about .020" thicker than the wall on the left side.

Note the difference in thickness between both sides of the barrel. In this case the bore wasn’t centered in the barrel. The wall on the right side of the picture is about .020″ thicker than the wall on the left side.

Prior to installing a Rem Choke system, the barrel wall thickness needs to be evaluated to make sure it is thick enough.  This is especially critical in cases such as this where the bore isn’t centered in the barrel.

More information on determining if a barrel wall is heavy enough for screw in choke tubes can be found in Choke tube installation and Removing a fixed choke from a shotgun barrel and installing a choke tube system.  Additionally, Brownells provides great information on measuring for screw-in choke tubes here.

The high-speed steel reamer used here will not cut a chrome lined barrel  (which isn’t a problem with a Remington Express barrel).  If you think a barrel is chrome lined, see if it takes cold blue.  If it does, it isn’t lined.  If it doesn’t it most likely is and you’ll need to remove the chrome lining prior to machining.

I'll be installing interchangeable choke tubes in the barrel.  In this case the Rem Choke style.  This is a Rem Choke reamer made by Dave Manson.  A bronze interchangeable pilot ensures it cuts true to the bore.

This is a Rem Choke reamer made by Dave Manson. A bronze interchangeable pilot ensures it cuts true to the bore.

There are a few different ways to set up the choke reaming operation in the lathe. The vent rib does complicate the situation since you cannot use a steady rest.  I originally planned on machining a aluminum disk with a broach cut for the rib.  The disk would be forced over the barrel and allow the steady rest to support it.  Unfortunately, my steady rest didn't have a large enough capacity to support it.  The barrel is held in a three-jaw chuck and the reamer is held in the tailstock.

There are a few different ways to set up the choke tube reaming operation on the lathe. The vent rib does complicate the situation since you cannot use a steady rest. I originally planned on machining a aluminum disk with a broach cut for the rib. The disk would be forced over the barrel and allow the steady rest to support it. Unfortunately, my steady rest didn’t have a large enough capacity to support it. The barrel is held in a three-jaw chuck and the reamer is held in the tail stock.

The lathe is run at 70 RPM, the slowest speed on this lathe and slowly fed with plenty of cutting oil.  The reamer is frequently removed, cleaned and lubricated.  When the reamer gets to its full depth, the cutter squares the muzzle.  This leading edge of the muzzle should be cut back to align with the vent rib base as shown in the photo above.

The lathe is run at 70 RPM, the slowest speed on this lathe and slowly fed with plenty of cutting oil. The reamer is frequently removed, cleaned and lubricated. When the reamer gets to its full depth, the cutter squares the muzzle. The leading edge of the muzzle should be cut back to align with the vent rib base as shown in the photo above.

The choke threads are cut with this Manson choke tap.  It is guided by the same bushing used with the reamer.

The choke threads are cut with a Manson choke tap. It is guided by the same bushing used with the reamer.

The barrel is secured vertically in a Multi-Vise with padded jaws.  The lubricated tap is used to cut the threads for the choke tube.

The barrel is secured vertically in a Multi-Vise with padded jaws. The lubricated tap is used to cut the threads for the choke tube.

Once the threads are cut the area is cleaned with compressed air.  A choke tube is test fit to make sure everything worked out.  Note the excess vent rib protruding over the front the of muzzle.

Once the threads are cut the area is cleaned with compressed air. A choke tube is test fit to make sure everything worked out. Note the excess vent rib protruding over the front the of muzzle.

The barrel is once again mounted vertically.  A large file is used to remove the majority the excess rib.

The barrel is once again mounted vertically. A large file is used to remove the majority of the excess rib.

A smaller file finishes the cut.  I also use it to break the sharp edges off the front and sides of the rib.

A smaller file finishes the cut. I also use it to break the sharp edges off the front and sides of the rib.

The barrel will be drilled and tapped for a 6-48 bead.  The barrel is set in the mill vise on a set of parallels.

The barrel will be drilled and tapped for a 6-48 bead. The barrel is set in the mill vise on a set of parallels. Prior to placing the barrel in the mill the choke tube is removed.

The vent rib is set level.

The vent rib is set level.

An edge finder is used to located the center and front edge of the rib.

An edge finder is used to located the center and front edge of the rib.

Shotgun beads are installed in both blind and through-type holes.  In this case, there is ample material for a blind hole installation.  However, since this gun is equipped with choke tubes, I decided to install the bead sight with a through hole since it will be covered by the choke (I avoid blind holes whenever I can).

A center drill is used to located the bead sight.

A center drill is used to spot the hole.

A #32 drill bit is used to cut the tap hole.

A #32 drill bit is used to cut the tap hole.

The tap is secured in in a tap handle and aligned over the hole with a spring loaded guide.

The tap is secured in in a tap handle and aligned over the hole with a spring loaded guide.

Success.  Once a bead is screwed in, this sight is ready for the field.

Success! Once the bead and choke tube are screwed in, this barrel is ready for field use.

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