"blueprinting" the action

Edmond_Dantes

August 16, 2005 15:24

what exactly is blue printing the action? in regards to a bolt rifle.

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  nononsense

  August 16, 2005 16:54

  What does blueprinting mean?
  
  Blueprinting refers to the machining performed on an action to make all of the machined surfaces nearly perfectly true to the bolt raceway. Production machining tolerances are generally 0.005" plus or minus. When blueprinting an action we bring those tolerances to a maximum of 0.0001" plus or minus. This is done by a machinist on a precision lathe equipped with a 4 jaw independent chuck. The receiver is centered in a truing sleeve that is adjustable by means of 4 front and 4 rear jaws, the rear having 2 locations (for long & short actions). Centering the receiver in the truing sleeve is accomplished by inserting a mandrel into 2 perfectly fitting bushings that have been inserted into the 2 bearing surfaces of the bolt raceway, and using 2 test indicators placed at opposite ends of the exposed mandrel end achieving axial alignment. When both indicators show .0001" or less run out at the same time & in the same rhythm you have perfectly aligned the center line of the bolt raceway axis with the lathes rotating axis. The receiver face, and the receiver locking lugs are cut at exactly 90 degrees to the bolt raceway line. The receiver threads are then single point re-cut so that they are also true to the bolt raceway line. The receiver way is polished for smooth bolt travel. The bolt is then put in a precision bolt fixture that insures that the bolt is centered on the firing pin hole. The fixture is then centered in a 4 jaw lathe chuck with test indicators, and the bolt face and the locking lugs are then cut true. The bolt and receiver locking lugs are lapped to mate the surfaces insuring 95% plus contact at exactly 90 degrees to the bore line. The firing pin spring channel is reamed & honed which reduces spring drag and shortens lock time.
  
  
  Here are 2 articles that explain the complete process with photo illustrations:
  
  http://www.findarticles.com/p/articles/mi_qa3623/is_199805/ai_n8791378
  
  http://www.vandykerifles.com/blueprint.htm
  
  Best.

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  jdyer

  August 16, 2005 16:59

  Related question - so what have you got when you've done all this "blueprinting" the action stuff? Does an average everyday hunting/shooting Joe need to care about it?

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  v35

  August 16, 2005 17:06

  No, but the target or varmint shooter will have the best basis to build a very accurate rifle.

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  Edmond_Dantes

  August 17, 2005 05:32

  thanks for the great answer. i saved those links, as i am absorbing all i can about precision shooting.
  again, many thanks

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