Blue-printing
Blue printing an action is a term we use to mean, “to make exactly like the intensions of the blue print”. In a blue print you have reference points in the drawing that all of the drawing’s components refer to by being parallel, perpendicular or angular to.
In the case of a Remington 700 Action there is a centreline. Every component of the rifle will reference to this centreline. It serves as the centreline of the bolt-way and the centreline of the threads. It should also be the same centreline of the bolt body and the firing pin hole.
The receiver face and the lugs are to be exactly perpendicular to this centreline as is the bolt face and recoil lugs on the bolt body.
In order to produce an affordable action, tolerances must be compromised and the manufacturing process closely scrutinised to yield marketable product and yet maintain a certain amount of affordability. We believe Remington do a very good job of this by producing a wonderful out of the box rifle. Unfortunately these compromises do not produce perfect actions. In order to achieve extreme accuracy there can be no compromises, it is either perfect or it is wrong.
When we blue print an action we make it as perfect as we can measure. All of our barrel work and action work is done in a independent 4 jaw chuck and indicated in till there is “0” run out.
We start by correcting all of the inconsistencies of the bolt itself. We bore out the firing pin hole and insert a plug or bushing. After the bushing is installed the bolt face is cut perfectly perpendicular with the centre line of the bolt.
Next the firing pin hole is re-drilled perfectly in the centre to a reduced diameter of .0625". Then the diameter of the firing pin nose is reduced to .0620". This smaller firing pin hole greatly increases the support of the primer and will enable it to withstand much higher pressures. The rear face of the recoil lugs in the receiver is then re-cut to be parallel with the bolt face and perpendicular to the bolt centreline.
Now we move on to the action. First we de-bur and hone the bolt-way so that we can easily slide it over the appropriate mandrel chosen from a set in incremental diameters. The appropriate mandrel is placed in a four jaw chuck and indicated to “0” run out. The action is then slid over the mandrel and a split sleeve with draw screws for tightening is place around the action.
We then make a lathe cut on the sleeve so that the outside diameter of the sleeve is on the exact same centre line of the mandrel which is on the centreline of the action. Removing the receiver with the mandrel going through it and the sleeve tightened around it, we then centre onto the sleeve that is around the action with the threaded end out and indicate off the mandrel. After the mandrel has been indicated in, we can slide it out of the action.
The action is now turning in the lathe on its true centreline with easy access to the threads, lugs and face. The original threads appear to be cut with a tap. If you have ever tapped a hole you know that it is impossible to start them absolutely perfect. Whatever the process used to cut the threads, when checked against the bolt way there always seems to be .004” to .008” of run-out on a centreline that deflects from the centre line of the action.
From the factory the receivers are threaded 1.0625 X 16 TPI. With a very sharp single point carbide tool we re-cut them to 1.075 X 16 TPI (that’s just enough to clean them up completely and establish a new standard). On the same set up the recoil lugs are re-cut and the receiver face is re-cut.
Finally the recoil lug is bored out to accommodate the larger thread size and is ground to have exactly parallel sides. Now everything is true to the intensions of the blue print.
The process described is somewhat of an oversimplification. There is a great deal of set up and lots of indicating. We don’t make any cuts until we are convinced that “0” run out has been achieved. As for the barrel we take just as much care cutting the barrel to mate with the now perfect action.