Re: Minimum effective range for a ladder test?
Sure, glad to help.
While shooting an Audette Ladder the trigger must be broken at exactly the same POA on every shot for the test to have meaning. You're trying to identify the load ranges that the barrel throws bullets to generally the same POI. You want that "group" or node to have as little vertical dispersion as possible. You also want to identify charge weight ranges that the barrel is throwing bullets haphazardly so you can stay away from them.
If your <span style="font-style: italic">shooting skill </span>throws bullets haphazardly, how will you know the culpret for the miss? You or the load?
If your skill is at the level that makes the results of ANY Audette questionable, why even shoot one?
I agree that a known one hole rifle/load will help an accomplished shooter identify the problem. My point was that if the guy's skill level was low, that even the one hole rifle/load may not help him hit anything any better than factory ammo. He certainly won't shoot as well as the rifle can.
As far as shooting an Audette at 100 yards to identify "nodes", I'm sure it can be done but reading the test will be a lot more difficult. ALL of the impacts will be very close together (fired from a good rifle barrel) and actually figuring out the node will be a chore and probably a guess. If you shoot the Audette at long range, the "nodes" will be much more evident and can be identified immediately without a micrometer.
My method is:
1. Shoot Audette at long range. Longer the better. No wind is better.
2. Identify consecutive shots with virtually the same POI and minimal vertical.
3. Load 5 of each of the loads in the node.
4. Shoot groups at any range your skill level allows with the loads.
5. Pick the best load from the groups.
6. Adjust seating depth (if even necessary) to fine tune.
Here's a recent Audette shot at 600 yards:
Loaded the 4 loads in the "node" and shot them...
Shots 14, 15, and 16 were an upper velocity node but too close to max for me and show more vertical. The barrel at those charge levels is less tolerant. I always choose the node with the least vertical.
The flat "node" DOES mean you've found your magic. Bullets impact at different levels not only because of gravity but also because of barrel harmonics; where the barrel happens to be pointing due to many different vibrations when the shot leaves the muzzle. The Audette Test helps identify the tolereable charge weight range for the barrel's best accuracy. The bullet is either exiting the muzzle at or just before its uppermost swing or visa versa. The barrel is "quiet" in movement or at point where it is in slow transition.
I've never seen or shot a "flat ladder". Everyone I've shot or seen shot, strings vertically.
The long range Audette Ladder works it all out.