Turning a sporter contour rifle barrel from a blank

Sporter contour rifle barrels have a radius cut by the shank (“E” in the diagram below).  This is different from straight tapered barrels typically encountered on match rifles.  Sporter contours are frequently used on hunting rifles where weight savings is a primary concern.  The radius cut allows a great amount of material to be removed as opposed to a straight taper.

For comparison purposes, the table below from Brownells, lists the profiles and weights of the Shilen barrels they sell.

brownells shilen profile chart complete

Note that profiles #1-#5 are sporter contours and profiles #6-#9 are straight tapers.  The heaviest sporter contour typically encountered is the Factory Remington 700 Varmint or Sendero profile, and is not shown on the table above.

In this post I’ll be turning down a Green Mountain Barrels chrome moly blank to a (slightly modified) Remington Varmint Contour.  The barrel will be used for a Remington 700 chambered in 7.62x39mm Russian, so I purchased one of Green Mountain’s .308″ bore, .310″ groove, 1:9.5 twist barrel blanks.

I ordered the following items from Brownells for this project:

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

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Any modifications made to a firearm should be made by a licensed gunsmith. Failure to do so may void warranties and result in an unsafe firearm and may cause injury or death.

Modifications to a firearm may result in personal injury or death, cause the firearm to not function properly, or malfunction, and cause the firearm to become unsafe.

7.62x39 green mountian unturned 310 groove blank

The blank is 1.375″ in diameter and 24″ long.  Quite a heavy and impressive piece of steel.

310 blank in chuck

The blank is mounted in a four jaw chuck and indicated to the bore.

60 degree piloted counterbore in 310 barrelA piloted 60 degree center drill is used to form a mating surface for the live center.

barrel ready for centerNote the 60 degree counterbore left by the center drill.

profiling set up

The barrel is now mounted between centers.  I am looking for a finished barrel length of 16″ long, so I will be profiling 17″ of the blank.  I will be using the rest of the barrel for a barrel length and velocity experiment; this excess material is in the headstock.  The live center in the tailstock supports the chamber end of the blank.

turning the profile between center note feeds and speeds

I don’t work on chrome moly barrel as much as I work on stainless.  As any machinist will tell you, speeds and feeds are key when machining.  On this pass, I was experimenting with spindle speed.  On the left the spindle speed was 220 RPM, on the right 360 RPM, all other settings were the same.  Note the superior finish on the right side of the cut.

heavy profile cuts continued for rem varmint contour

A factory Remington Varmint contour barrel has a slight taper on the tube.  It measures .950″ in front of the shank, and .850″ at 26″.  In this case, I’ll be cutting the entire barrel forward of the shank, .950″.  I like to take a heavy pass, .040-.050″ at a time.  Since I don’t have a lot of distance between centers, I didn’t need a steady or follow rest to get decent results.  I’m cutting from left to right, towards the tail stock.  This is because I don’t have a shoulder to prevent the barrel from sliding into the headstock.

pile of lathe shavings

All the turning makes for an impressive pile of shavings!

measuring blank for comparison

To determine the dimensions for the shank, I measure a barrel that I’d like to copy.  This is a Bartlein with a Rem Varmint profile from another project.  I mark the barrel in .100″ increments forward for the straight shank.  I then record the measurements.

measurement sheet

The measurements allow me to formulate a cut list needed to duplicate the profile.  In this case, the list shows how far in I need to cut from the outside diameter of the blank.  The number in the left column indicates how far from the shank I need to stop the cut.  For instance, 1.5 indicates I need to take a cut .088″ deeper than the shank and stop 1.500″ from the beginning of the shank.

step cuts on profile

This is what the barrel looks like after the series of step cuts.

step cuts second view

Another view of the step cuts.  The black line indicates the end of the straight part of the shank.

file smooths cuts

A lathe file allows me to smooth out the profile.

end of muzzle

This is the muzzle section of the barrel that was held in the chuck when the profile was turned.  As stated earlier, I’d normally just chop it off, but I want to get some barrel length and velocity data with it.  Before leaving the lathe, I’ll turn it down closer to the finished diameter of the barrel.

blank off of lathe

The barrel when it leaves the lathe.

barrel spinner

The barrel is mounted in a barrel spinner.  The barrel spinner supports the barrel between two ball bearings with a set of nylon centers.  You can make or buy a barrel spinner, this one is a Clymer I ordered from Brownells.

barrel spinner on belt

The barrel is held in the spinner and run against a belt grinder.  I start at 120 grit and gradually move up to 240, 320 and 400 grit belts.

left hand slows spinner

My left hand is used to slow down the rotation of the barrel as it is held in the spinner.

finsihed remington Varmint barrel blank

The finish barrel barrel looks pretty sharp.  A big change from when we started.


side 1 M700 7.62x39

A view of the barrel installed on a Remington 700 chambered in 7.62×39!