6.8 SPC Chamber Drawings

Below are sections of the chamber drawings of the various 6.8 x 43 mm chambers showing the area discussed in the article.


Original SAAMI Chamber showing the angle error.  On the drawing above, based on the dimensions specified in the drawing the angle works out to 70 55':.

Original second version SAAMI Chamber ("SPC II") showing more generous specs
but continuing the angle error.  On the drawing above  the based on the dimensions specified in the drawing the angle works out to 71 30'
 

* I have recently been informed that the SPC II reamers currently (2/09) being cut now actually have a 45 deg angle, which would mean that the horizontal measurements would be .105 and .0905", giving .01495" 

DMR (Designated Marksman Rifle) chamber showing improved angle.  If you do the
math you get an angle of 35 1'.  Note the tighter neck (.305") and throat (.277") dimension.  There have been several variations of this drawing circulated with the angle varying from 25 to 37 degrees. and all associated with barrels using the 5R rifling form.

Thanks to Tim W. for supplying the drawings


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Disclaimer

As far as I know all the information presented above is correct and I have attempted to ensure that it is. However, I am not responsible for any errors, omissions, or damages resulting from the use or misuse of this information, nor for you doing something stupid with it. (Don't you hate these disclaimers? So do I, but there are people out there who refuse to be responsible for their own actions and who will sue anybody to make a buck.)

Updated 2009-02-10