What is nock indexing or nock tuning?

Nock indexing is the deliberate orientation of your arrow's nock — and therefore your fletching — relative to the bow at the moment of the shot. It is not a mystery; it is geometry. When you place the arrow on the string, the nock can rotate to any position around the shaft's long axis. Nock tuning is the practice of finding and setting the specific rotation that produces the most consistent flight from your particular bow with your particular arrow.

The practical concern is this: your vanes or feathers, as they clear the riser and rest, will behave differently depending on whether they strike plastic, pass through air, or graze a launcher blade at a slight angle. A poorly indexed nock sends a different vane through that disturbance on every shot unless you control it. The index cock vane — the one that stands proud of the shelf or rest — is conventionally set either pointing straight up, straight down, or to the side, depending on the rest type. For a drop-away rest, cock vane down or to the side is common. For a shoot-through rest or a Berger-style button, cock vane up or to the side is typical. The right answer is whichever orientation causes your arrow to exit the bow without vane contact, verified by powder spray or arrow-wrap inspection.

Nock tuning goes a step further: you paper-tune or walk-back tune first to establish a baseline, then you rotate the nock in small increments — as little as a few degrees at a time — and observe whether groups tighten or point-of-impact shifts. The nock itself should snap onto the string with quiet, consistent resistance — not so tight it delays release, not so loose it falls free. A nock that requires more than a firm finger-flick to remove is generally too tight; one that falls under the arrow's own weight is too loose. Some shooters mark their preferred index position on the shaft in permanent ink once they have found it, so the orientation can be restored after any nock replacement.

The fourth feather, naturally, makes this arithmetic more elegant: with four vanes at ninety degrees, the relationship between the index vane and the string is uniform in every quadrant. The Committee's preferred three-vane arrangement means the index vane and its neighbors are not equidistant, which is a geometric asymmetry the grey catalog declines to discuss. I have noted this in the margin of the Codex for forty years.