Reloading ladder test: do you pick the tightest group or the lowest SD?

Neither one alone. Judge the groups and the velocity SD together, let the groups carry more of the weight, and use SD to throw out a step whose velocities are all over the place. Then confirm the finalist with a bigger group before you trust it.

Which group number: group size or mean radius?

Group size is set by your two worst shots, so one flier decides it. Mean radius averages every shot’s distance from the center of the group, so it describes the whole group. On a ladder, where every step is only a few shots, mean radius is the steadier number. See the worked example with the arithmetic in mean radius vs group size.

Tightest group or lowest velocity SD?

They answer different questions. The group says where the shots landed. Velocity SD says how consistent the speeds were. A low SD does not make a small group, and a small group on three shots can be luck. When they disagree, the step that holds up on both is the safer pick. A tight group at a step with a high SD is usually a good spot on a bad day, and a low SD with an average group is a consistent load that isn’t shooting small yet.

What if the velocity flat spot and the groups disagree?

Let the groups win. The flat spot (the stretch of charges that shoot about the same speed) is a tie-breaker, not the verdict. At a 100-yard test, Loadscope’s powder-ladder weighting is mean radius 40%, vertical SD 35%, velocity SD 20% and the velocity flat spot 5%, and it shifts toward velocity SD as the distance grows. More on reading a powder ladder and what a good velocity SD is.

Seating depth: which depth wins?

Seating depth shapes the group, not the speed, so judge it on the groups, mostly mean radius, with vertical spread counting for more as the distance grows. Look for a small range of depths that all shoot well, not one lucky number. See how to run a seating depth test.

Tuner: which setting wins?

A tuner doesn’t change velocity, so don’t score it on speed. Score each setting on vertical spread and mean radius, and look for a run of neighboring settings that all shoot well. See how to score a barrel tuner test.

How many shots before you trust either?

Three shots can screen out the obviously bad steps. They can’t pick a winner, because at that count luck is as big as the difference between two close steps. Take the one or two finalists and shoot a larger confirmation group. More in how many shots per charge.

What to ignore

• The single smallest group from three shots.
• The lowest SD from a three-shot string.
• The fastest step, on its own.
• One good step standing alone between two bad neighbors.

Discussion: how other handloaders decide