“Blueprinting” (Truing) a Remington 700 Action

December 23, 2014 Bill Marr Gunsmithing 0

Remington 700 short action receiver. The bolt has been helically fluted by Kampfeld Customs.
Truing a Remington 700 Action on a Lathe

“Blueprinting” or truing an action is the process used to square the critical surfaces of a bolt action rifle receiver prior to barreling.  This is done to enhance accuracy.

In a previous post I covered a method that did not require a lathe, using a specialized kit from Manson. Alternatively, a metal lathe can be used to perform the same task.

To view these posts, see:

Blueprinting a Remington 700 Action

Refreshing a poorly machined Remington 700 action

Those critical of the Manson style truing kits argue that taps and dies, no matter how stout, follow existing holes and do not provide the same results as single-point cutting the receiver on a lathe.

Here, I will be working on a new Remington model 700 short action with a .223 bolt face.  I will be truing the following surfaces:

  1. receiver ring
  2. receiver lugs
  3. minor diameter of the the receiver threads
  4. receiver threads
  5. front and rear faces of the bolt lugs
  6. bolt nose
  7. bolt face

This post will cover #1-4 in the list above.  To see how the bolt is trued, read Truing The Bolt On A Remington 700

Note: in addition to these steps, some gunsmiths will also ream the bolt hole to a larger diameter, sleeve the bolt, bush and recenter the firing pin hole.

I ordered the following items from Brownells:

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

The Remington 700 short action receiver. The bolt has been helically fluted by Kampfeld Customs.
The Remington 700 short action receiver. The bolt has been helically fluted by Kampfeld Customs.
This is a front view of the receiver prior to beginning the blueprinting process.
This is a front view of the receiver prior to beginning the blueprinting process.
All surfaces will be squared to the receiver's bolt hole. In order to indicate this on the lathe, the .701" receiver mandrel from LaBounty will be used.
All surfaces will be squared to the receiver’s bolt hole. In order to indicate this on the lathe, the .701″ receiver mandrel from LaBounty will be used.
La Bounty sells the receiver mandrels in a two piece set. .701" and .703". In this case, the .701" mandrel fit well, the .703" was too large for my application.
La Bounty sells the receiver mandrels in a two piece set. .701″ and .703″. In this case, the .701″ mandrel fit well, the .703″ was too large for my application. Alternatively, a set of tapered bushings and and rod can be used.
To hold the receiver in the lathe, I am using a chambering and truing fixture from Viper's Bench Rest. The fixture is held in the four jaw chuck and dial indicated in. You may notice the chuck is holding the fixture on the rounded surfaces, rather then the four milled flats. I have found this allows the lathe to have a solid grip on the fixture, the convex four jaw chuck jaws have a tendency to slip on the flats.
To hold the receiver in the lathe, I am using a chambering & truing fixture from Viper’s Bench Rest. The fixture is held in the four jaw chuck and dial indicated in. You may notice the chuck is holding the fixture on the rounded surfaces, rather then the four milled flats. I have found this allows the lathe to have a solid grip on the fixture, the convex four jaw chuck jaws have a tendency to slip on the flats.

The chambering & truing fixture that I am using has a series of brass tipped screws, located at 12, 3, 6 and 9 o’clock around the receiver.  Dial indicators and the mandrel are used to dial in the receiver, as shown in the photos below.

The action, with mandrel is inserted into the fixture, with the front of the receiver protruding from the front of the fixture. The receiver is then dial indicated in.
The action, with mandrel is inserted into the fixture, with the front of the receiver protruding from the front of the fixture. The receiver is then dial indicated in.
The indicator is then moved to the end of the mandrel to adjust the rear fixture screws (those closest to the chuck).
The indicator is then moved to the end of the mandrel to adjust the rear fixture screws (those closest to the chuck). Initial adjustments are made with a .001″ indicator, final adjustments are made with a .0001″ indicator.
With the receiver dialed in. The receiver ring is faced with a light cut. Note how part of the receiver is cut while part is still uncut. This shows how out of square it was to the bolt hole.
With the receiver dialed in. The receiver ring is faced with a light cut. Note how part of the receiver is cut while part is still uncut. This shows how out of square it was to the bolt hole.
I make another very light pass. Now the entire front of the receiver ring is squared.
I make another very light pass. Now the entire front of the receiver ring is squared.
The next step is to cut the front surfaces of the receiver lugs. I do this with a boring bar, again, taking very light passes. Note the lug after a light pass, bottom right side of the receiver.
The next step is to cut the front surfaces of the receiver lugs. I do this with a boring bar, again, taking very light passes. Note the lug after a light pass, bottom right side of the receiver.

I make the receiver lug cuts from the receiver wall in.  I have the DRO zeroed to the inside end of the receiver wall and take a series of light passes.

After another light pass, the receiver lugs are cut. Note the shiny surface, bottom left of the inside of the receiver.
After another light pass, the receiver lugs are cut. Note the shiny surface, bottom left of the inside of the receiver.
With a boring bar, I make a series of light passes to open up the minor diameter of the receiver threads. These will be cut .010" deeper.
With a boring bar, I make a series of light passes to open up the minor diameter of the receiver threads. These will be cut .010″ deeper- note the flat surfaces at crest, or top, of the threads.

Its critical you don’t allow the boring bar to move too deeply into the receiver.  My lathe has a DRO, before making any cuts, I set the maximum depth to “0.0000” and take caution to avoid cutting too deeply or crashing into a receiver lug.

The threading tool is positioned and aligned with the receiver and I take a series of light passes.
The threading tool is positioned and aligned with the receiver and I take a series of light passes.

Picking up the threads can be a little intimidating if you haven’t tried it before, however, it is not that difficult.  This is the process I used:

  1. Set up the lathe for threading operations.  In this case the threading tool is adjusted with a fish tail to cut square to the receiver, the lathe is set to cut 16 threads per inch (for the M700) and the lead screw is engaged.
  2. Set lathe to 70 RPM- that’s the slowest my lathe will go.
  3. Adjust threading tool so it will not make contact with the receiver.
  4. Turn on lathe, engage the half nut at the appropriate point on the threading dial (on my lathe this is an marked graduation for even thread pitches) and allow the threading tool to move two or three threads into the receiver then turn off the lathe.
  5. The compound, mine is set at 29.5 degrees, is then used in conjunction with the cross slide to adjust the tip of the threading tool into the root (or valley) of the thread. The thread is now located.

I used the cross slide on the lathe to adjust the depth of cut, .001″ at a time.  A gauge I had previously made (.013″ over std diameter) was periodically checked against receiver to determine with the proper depth of cut was achieved.

Once again, it is critical you don’t bump the threading tool into the receiver lugs or cut too deeply into the receiver.  I zeroed my DRO to prevent this, however, a dial indicator could be used as well.

This home made gauge, allows me to determine when the threads have been cut deep enough.
This home made gauge, cut .010″ oversize, allows me to determine when the threads have been cut deep enough.

Once the threads are cut to depth, the bolt surfaces need to be trued.  To see how the bolt is trued, Truing The Bolt On A Remington 700.  Finally, the action will be ready for a new barrel.

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