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Old April 10, 2013, 09:41 AM   #16
Bart B.
Senior Member
Join Date: February 15, 2009
Posts: 6,318
Most reloading data that's published is from barrels other than SAAMI speck velocity and pressure test barrels. Such SAAMI spec barrels can cost about 2 times as much as top level match grade barrels 'cause they're made to exact dimensional specs and tolerances for chamber and bore/groove dimensions.

So, the data's gonna be different in factory or aftermarket rifle barrels in shoulder fired rifles compared to fixed mounted ones in standard test receivers.

To say nothing of the differences in firing pin impact, lot differences for powder and primers and how the barrel's held. SAAMI specs require a fixed mount of a standard universal receiver and test barrel; it does not move backwards in recoil like shoulder fired rifles do. It's easy to get a 100 fps difference in muzzle velocity from person A to person B shooting the same rifle and ammo; they don't hold the rifle with the same force and angle to their bodies which also are not in the same position behind the rifle. Example is shown below.
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