Originally Posted by jmason
...does anyone "speed" sort brass? ...by chrono reading.
If we get and do all the right stuff to get:
*firing pin strikes with exactly the same force every one of some
*100 primers that detonate with the same time/temperature curve behind
*100 powder charges weighed to 0% spread sitting behind
*100 bullets with exactly the same jacket hardness and throat entry angle and
*fired when the powder's at the same temperature with
*the rifle being held with the same grip force and recoil-resistant directions
the powder alone won't produce a pressure curve repeatable enough to tell the difference between cases with a 0.5% weight spread. This alone assumes that all the cases have exactly the same metallurgy; the brass is homogenous enough that all cases with zero weight tolerance take up the same amount of volume in the chamber.
If one's ever tested primer's muzzle velocity shooting 17 caliber pellets (or BB's) from a .17 Remington with no powder in the case, you'll be surprized by the velocity spread they have themselves. Not to mention that those producing the lowest BB/pellet muzzle velocity will probably produce the best accuracy. Testing primers with normally loaded rounds ain't all that good. The powder's burning tolerances typically mask primer ignition curves.
All of which suggests there's too many variables to mask the velocity spread caused by a small case weight tolerance.
Firing pin striking force spread? Clamp a complete action with cocked bolt vertically in a vice, put a 3/8ths inch steel ball on the bolt face's firing pin hole then trip the trigger. Measure how high the ball goes up. Then figure out how to make 'em all go the same height. Then compare a 3 to 4 year old one kept on the pin against a new one of the same force rating. You may decide to replace 'em every 2 to 3 years.