OCW, Ladders and Seating Tests — Which Answers What

OCW looks for a charge band where the point of impact stays put as charge increases. Rounds are fired in round-robin order across the charge weights — one at each charge, then repeat — rather than all of one charge and then all of the next. That ordering matters: it distributes barrel heating, fatigue, and changing wind across all the charges rather than concentrating any of them on one step, which is a genuine methodological improvement over a naive ladder.

The output is a charge band, not a group size. The claim is that a load in the middle of a POI-stable band will be tolerant of temperature swings, small charge variation and component lot changes — which is a robustness claim, and a sensible one.

A velocity ladder fires increasing charges over a chronograph and looks for a flat spot — a region where velocity stops increasing proportionally with charge weight. The traditional interpretation treats that plateau as a node worth loading in the middle of.

⚠️ This one deserves scepticism. With the small shot counts typical of a ladder, apparent velocity flat spots are readily produced by ordinary shot-to-shot variation, and repeated ladders on the same rifle often put the flat spot in different places. If you use a velocity ladder, use it as one piece of evidence among several, and be suspicious of a flat spot that only ever appeared once.

A seating depth test holds the charge constant and varies the jump, looking for a depth where dispersion tightens. It answers a different question from any charge test: not how fast, but how the bullet enters the rifling.

The conventional order is charge first, seating second — settle a charge band, then fine-tune seating within it. That order exists because charge weight has the larger effect, and because it is the variable that governs pressure and velocity, which everything else is built on. ⚠️ Remember that seating longer can raise pressure, so a seating test is not a free variation on a settled charge; treat a significant seating change as something to re-verify.

There is no rule that you must run all three methods. If you want a robust hunting or field load, an OCW-style test for a stable band and then a confirmation batch is a complete process. If you are chasing the last fraction for competition and you own a chronograph, adding velocity statistics and a seating test is worth the components. Running every method on every rifle is how people spend a barrel's life on development and never shoot a match.