Clemson
Senior Member
I am a working gunsmith. I see suggestions fairly often that owners of inaccurate rifles have the "actions blueprinted." I'm not sure we are all on the same sheet of music in understanding what blueprinting is and how it affects accuracy. First off, let's pick a rifle action type. Blueprinting is different for different actions. A Remington 700 is a good place to start. To blueprint a Remington 700, the barrel must be removed, and all parts that attach to the receiver are likewise removed. Machining of the action then takes place to insure that the action threads are exactly parallel to the bolt raceway. That can be done by single point machining of the threads with the receiver dialed into a lathe fixture that holds it in alignment with the axis of the lathe. Alternately, it can be done with bushings that fit the bore of the receiver precisely and which align a tap that then recuts the threads. The end result is exactly the same. The receiver face is cut to be perpendicular to the bore and dead flat.
Now we have a receiver with the threads parallel to the bolt raceway. For a hunting rifle, I then lap the bolt lugs into even fit on both sides of the bolt. There are additional steps to insure a tight fitting bolt that can be taken with a benchrest gun, but, honestly, if you are building a benchrest gun, you are miles ahead to start with a custom "clone" action (Panda, Sturgeon, etc.).
The receiver threads are now oversized by about 0.010 inches. The old barrel will be a sloppy fit, so we need a new barrel with newly cut threads that are oversized to fit the receiver. Also, our recoil lug won't fit the new barrel tenon, so we need a new one. That gives us the opportunity to surface grind both sides to insure a great fit up to the receiver and the barrel shoulder. Thus ends our blueprinting.
Obviously, this is not a trivial undertaking. You are not only recutting the receiver, you are replacing the entire barrel. You can't "blueprint" the receiver to the existing barrel. Rant over -- Shoot straight!
Bill Jacobs
Now we have a receiver with the threads parallel to the bolt raceway. For a hunting rifle, I then lap the bolt lugs into even fit on both sides of the bolt. There are additional steps to insure a tight fitting bolt that can be taken with a benchrest gun, but, honestly, if you are building a benchrest gun, you are miles ahead to start with a custom "clone" action (Panda, Sturgeon, etc.).
The receiver threads are now oversized by about 0.010 inches. The old barrel will be a sloppy fit, so we need a new barrel with newly cut threads that are oversized to fit the receiver. Also, our recoil lug won't fit the new barrel tenon, so we need a new one. That gives us the opportunity to surface grind both sides to insure a great fit up to the receiver and the barrel shoulder. Thus ends our blueprinting.
Obviously, this is not a trivial undertaking. You are not only recutting the receiver, you are replacing the entire barrel. You can't "blueprint" the receiver to the existing barrel. Rant over -- Shoot straight!
Bill Jacobs