Dannix
12-27-2010, 11:49 PM
I was looking for 6.8 SPC trajectory numbers the other day and came across this page (http://www.frfrogspad.com/68spc.htm) and a "various chamber designs" page (http://www.frfrogspad.com/68chambers.htm) linked there, quoted below.
So what sort of chamber is more bullet friendly than others? Is one of the below chambers a lead friendly chamber, or would another need to be speced for an ideal boolit 6.8SPC chamber? Would an ideal boolit chamber compromise j-word performance somehow?
Also, barrels. What's the rational for choosing between one groove option over another?
http://www.frfrogspad.com/68sam.jpg
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':.
http://www.frfrogspad.com/68sam2.jpg
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"
http://www.frfrogspad.com/dmr.jpg
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.
So what sort of chamber is more bullet friendly than others? Is one of the below chambers a lead friendly chamber, or would another need to be speced for an ideal boolit 6.8SPC chamber? Would an ideal boolit chamber compromise j-word performance somehow?
Also, barrels. What's the rational for choosing between one groove option over another?
http://www.frfrogspad.com/68sam.jpg
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':.
http://www.frfrogspad.com/68sam2.jpg
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"
http://www.frfrogspad.com/dmr.jpg
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.