Arrow spine for a 70 lb compound at a 31 inch arrow with a 100 grain point: a 300 spine (band 300-340), plus the 350 grain minimum weight. Sourced.
Updated 05 September 2026.
What arrow spine for 70 lb draw at a 31 inch arrow
The starting spine for a 70 lb draw at a 31 inch arrow with a 100 grain point, and the weight floor.
| Draw weight | 70 lb |
|---|---|
| Arrow length | 31 in (cut, nock groove to shaft end) |
| Point weight | 100 gr |
| Recommended spine | 300 (published band 300-340) |
| Minimum total weight | 350 gr, from the 5-grains-per-pound floor |
Easton 5mm Axis carbon arrow shaft (300 spine)
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A 70 lb bow at a very long 31 inch arrow flexes more than the 29 or 30 inch cuts, holding it firmly at a 300 spine. Long-draw shooters at heavy weights are the reason 300 is the core hunting spine.
Spine is a starting point, not a guarantee, because a 340 from one brand can differ from another. Confirm on your arrow maker's chart at 31 inches and 70 pounds, or bare-shaft test before cutting a dozen.
Whatever spine you land on, keep the finished arrow at or above 350 grains total, the 5-grains-per-pound floor, so the bow is not shooting dangerously light.
The rules behind this pick
Questions and answers
What arrow spine for 70 lb draw at a 31 inch arrow?
For a 70 lb draw at a 31 inch arrow with a 100 grain point, start with a 300 spine (the 300-340 band), and keep the finished arrow at or above 350 grains total.