what makes a load "accurate"

[Deleted old_dood]

is it the load that produces a given velocity range, or a given pressure. if two different powder/primer combinations provide the same velocity or pressure will they both show the same accuracy? just something I'm thinking about.

 

[Alex Wheeler]

It is the point when the bullet exits the muzzle in relation to the barrels vibration modes.

 

[savagedasher]

I'll also add that equal muzzle velocity doesn't necessarily mean the bullet will exit the muzzle at the same point in the harmonic cycle of the barrel. Different powder/primer combinations can be used to generate very close to the same muzzle velocity, but the acceleration of the bullet in the bore, and therefore, the time it spends in the bore, can be quite different, even though it emerges at the same velocity. Therefore, it may be necessary to re-adjust the timing of the bullet to optimize grouping when changing powder or primers, even if you achieve the same final muzzle velocity as another load that shoots well.

+ 1 That is why barrel time can be way off. That is also why tuners work. Larry

 

[joshb]

All of the above, plus: "Some guy" has painfully reformed his brass to .0001 specs. Spent countless range sessions, working on .01 powder graduations, with various powders, and COLs to the .001 degree, then tested and retested. All loads for 1 gun. I might ask "What load works?" I then have to go through the same work, for my gun. The answer is a starting reference, only.