Crossbow Bolt Straightness: Definition

Crossbow Bolt Straightness in plain terms

Crossbow Bolt Straightness meaning: Bolt straightness is how far a crossbow bolt shaft may bend from true, written in thousandths of an inch, such as .001 or .004.

Also called: straightness tolerance, shaft straightness, bolt straightness rating, .001 straightness

Bolt straightness is the maximum amount a bolt shaft is allowed to deviate from perfectly straight, measured in thousandths of an inch along its length. A shaft rated .001 may bend no more than one thousandth of an inch; a shaft rated .004 is allowed four times as much.

Manufacturers usually quote straightness alongside weight tolerance, which is how closely bolts in a pack match each other in grain weight, for example within 1 grain per pack or within 5 grains per dozen. Together the two numbers describe consistency: how alike each bolt in your quiver will fly.

Straightness is a manufacturing tolerance, not a measure of quality on its own. A .004 bolt can shoot very well at normal hunting distances; tighter tolerances matter more as distance grows and as you try to shrink groups.

Straightness and weight tolerance of bolts I have reviewed

Why it matters

A bent bolt does not leave the rail the same way as a straight one, so it lands in a slightly different place. Across a pack, small differences in straightness and weight show up as a larger group, especially at 40 yards and beyond.

It also changes what a bad group means. With tightly matched bolts, a flyer is more likely to be you or the crossbow; with looser bolts, some spread is built in. That matters when you are sighting in or deciding whether a crossbow shooting high, low, left or right has a real fault.

Tighter tolerances cost more per bolt. The TenPoint CenterPunch HPX at .001 and ±1 grain sits at the premium end, while .004 bolts such as the Wicked Ridge Match 400 cost far less and suit most hunting distances.

How to read it on a spec sheet

• Smaller numbers are straighter: .001 is tighter than .003, which is tighter than .004.
• Read weight tolerance next to straightness; "per pack" and "per dozen" are not the same basis.
• Check whether the figure is for the bare shaft or the finished bolt with nock and insert.
• Treat "undocumented" or missing tolerances as looser rather than equal.
• Compare bolts at the same length and weight, which still have to meet your crossbow's minimums.

Common mistakes

• Paying for .001 bolts to fix groups that are really caused by cocking unevenly or a loose scope.
• Mixing bolts from different packs or models and expecting them to group together.
• Ignoring a bolt that has hit something hard; impact can bend a shaft beyond its rating.
• Choosing on straightness alone and ignoring the crossbow's required length, weight and nock.
• Assuming a cheap bolt is unsafe because of a looser tolerance; damage, not tolerance, is the safety issue.

Checking your bolts at home

1. Number each bolt so you can track which one flies off.
2. Spin each bolt on a flat surface or between your fingers and watch for wobble.
3. Weigh bolts with their tips if you have a grain scale and note any outliers.
4. Shoot groups and record which numbered bolts land outside the group.
5. Retire any bolt that is cracked, bent or consistently off, rather than mixing it back in.

In my testing

Straightness and weight tolerance are recorded from the manufacturer for each bolt I review, and I note how consistently the pack groups during accuracy testing. The figures in the table come from those reviews. How I test.

See it in our reviews

• TenPoint Lighted Pro Elite 400 — rated 4.5/5
• Carbon Express PileDriver — rated 4.2/5